[Federal Register Volume 73, Number 228 (Tuesday, November 25, 2008)]
[Proposed Rules]
[Pages 71788-71826]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-27524]



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Part III





Department of the Interior





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Fish and Wildlife Service



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50 CFR 17



Endangered and Threatened Wildlife and Plants; 12-Month Finding on a 
Petition To List the Northern Mexican Gartersnake (Thamnophis eques 
megalops) as Threatened or Endangered With Critical Habitat; Proposed 
Rule

  Federal Register / Vol. 73, No. 228 / Tuesday, November 25, 2008 / 
Proposed Rules  

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R2-ES-2008-0065; MO 9221050083-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List the Northern Mexican Gartersnake (Thamnophis 
eques megalops) as Threatened or Endangered with Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list the northern Mexican gartersnake 
(Thamnophis eques megalops) as threatened or endangered with critical 
habitat under the Endangered Species Act of 1973, as amended (Act). The 
petitioners provided three listing options for consideration by the 
Service: (1) Listing the U.S. population as a Distinct Population 
Segment (DPS); (2) listing Thamnophis eques megalops throughout its 
range in the United States and Mexico based on its rangewide status; or 
(3) listing Thamnophis eques megalops throughout its range in the 
United States and Mexico based on its status in the United States. On 
the basis of the best scientific and commercial information available, 
we find that listing the northern Mexican gartersnake as threatened or 
endangered throughout its range in the United States and Mexico, based 
on its rangewide status, is warranted under the Act, due to the present 
or threatened destruction, modification or curtailment of its habitat; 
predation; and the inadequacy of existing regulatory mechanisms. 
Currently, listing is precluded by higher priority actions to amend the 
Lists of Endangered and Threatened Wildlife and Plants. Upon 
publication of this 12-month petition finding, the northern Mexican 
gartersnake will be added to our candidate species list. We will 
develop a proposed rule to list the northern Mexican gartersnake as our 
priorities allow. Any determination on critical habitat will be made 
during development of the proposed rule.

DATES: The finding announced in this document was made on November 25, 
2008.

ADDRESSES: This finding is available on the Internet at http://www.regulations.gov at Docket Number FWS-R2-ES-2008-0065. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours at the U.S. 
Fish and Wildlife Service, Arizona Ecological Services Office, 2321 
West Royal Palm Road, Suite 103, Phoenix, AZ 85021-4951. Please submit 
any new information, materials, comments, or questions concerning this 
finding to the above address.

FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor, 
Arizona Ecological Services Office (see ADDRESSES), telephone 602-242-
0210. If you use a telecommunications device for the deaf (TDD), please 
call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.), requires 
that, for any petition containing substantial scientific and commercial 
information indicating that listing may be warranted, we make a finding 
within 12 months of the date of receipt of the petition on whether the 
petitioned action is: (a) Not warranted, (b) warranted, or (c) 
warranted, but immediate proposal of a regulation implementing the 
petitioned action is precluded by other pending proposals to determine 
whether species are threatened or endangered, and expeditious progress 
is being made to add or remove qualified species from the Lists of 
Endangered and Threatened Wildlife and Plants. Section 4(b)(3)(C) of 
the Act requires that we treat a petition for which the requested 
action is found to be warranted but precluded as though resubmitted on 
the date of such finding; that is, requiring a subsequent finding to be 
made within 12 months. We must publish these 12-month findings in the 
Federal Register.
    On December 19, 2003, we received a petition dated December 15, 
2003, requesting that we list the northern Mexican gartersnake as 
threatened or endangered, and that we designate critical habitat 
concurrently with the listing. The petition, submitted by the Center 
for Biological Diversity, was clearly identified as a petition for a 
listing rule and contained the names, signatures, and addresses of the 
requesting parties. Included in the petition was supporting information 
regarding the species' taxonomy and ecology, historical and current 
distribution, present status, and actual and potential causes of 
decline. We acknowledged the receipt of the petition in a letter to Mr. 
Noah Greenwald, dated March 1, 2004. In that letter, we also advised 
the petitioners that, due to funding constraints in fiscal year (FY) 
2004, we would not be able to begin processing the petition at that 
time.

Previous Federal Actions

    The Mexican gartersnake (Thamnophis eques) (which included the 
subspecies megalops) was placed on the list of candidate species as a 
Category 2 species in 1985 (50 FR 37958). Category 2 species were those 
for which existing information indicated that listing was possibly 
appropriate, but for which substantial supporting biological data to 
prepare a proposed rule were lacking. In the 1996 Candidate Notice of 
Review (February 28, 1996; 61 FR 7596), the use of Category 2 
candidates was discontinued, and the northern Mexican gartersnake was 
no longer recognized as a candidate.
    On May 17, 2005, the petitioners filed a complaint for declaratory 
and injunctive relief, challenging our failure to issue a 90-day 
finding in response to the petition as required by 16 U.S.C. 
1533(b)(3)(A) and (B). In a stipulated settlement agreement, we agreed 
to submit a 90-day finding to the Federal Register by December 16, 
2005, and if substantial, submit a 12-month finding to the Federal 
Register by September 15, 2006 (Center for Biological Diversity v. 
Norton, CV-05-341-TUC-CKJ (D. Az)). The settlement agreement was signed 
and adopted by the District Court of Arizona on August 2, 2005.
    On December 13, 2005, we made our 90-day finding that the petition 
presented substantial scientific information indicating that listing 
the northern Mexican gartersnake (Thamnophis eques megalops) may be 
warranted, but we did not discuss the applicability of any of the three 
listing scenarios that were provided in the petition. The finding and 
our initiation of a status review was published in the Federal Register 
on January 4, 2006 (71 FR 315).
    On September 26, 2006, we published a 12-month finding that listing 
of the northern Mexican gartersnake was not warranted because we 
determined that not enough information on the subspecies' status and 
threats in Mexico was known at that time (71 FR 56227). On November 17, 
2007, the petitioners filed a complaint for declaratory and injunctive 
relief pursuant to section 11 of the Act (16 U.S.C. 1540), seeking to 
set aside the 12-month finding. Additionally, a formal opinion was 
issued by the Solicitor of the Department of the Interior, ``The 
Meaning of In Danger of Extinction Throughout All or a Significant 
Portion

[[Page 71789]]

of Its Range'' (U.S. DOI 2007), which provides further guidance on how 
to conduct a detailed analysis of whether a species is in danger of 
extinction throughout a significant portion of its range. In December 
2007, the Service withdrew the September 26, 2006, 12-month finding to 
consider the new ``Significant Portion of the Range'' policy. In a 
stipulated settlement agreement with the petitioners, we agreed to 
submit a new 12-month finding to the Federal Register by November 17, 
2008 (Center for Biological Diversity v. Kempthorne, CV-07-596-TUC-RCCJ 
(D. Az)). The settlement agreement was signed and adopted by the 
District Court of Arizona on June 18, 2008.
    This notice constitutes a new 12-month finding for the petition to 
list the northern Mexican gartersnake as threatened or endangered. The 
petitioners described three potentially listable entities of 
gartersnake for consideration by the Service: (1) Listing the U.S. 
population as a Distinct Population Segment (DPS); (2) listing 
Thamnophis eques megalops throughout its range in the United States and 
Mexico based on its rangewide status; or (3) listing Thamnophis eques 
megalops throughout its range in the United States and Mexico based on 
its status in the United States. Because we found that listing the 
northern Mexican gartersnake rangewide was warranted, there was no need 
to conduct any further analysis of the remaining two options, which are 
smaller geographic entities and are subsumed by the rangewide listing.

Biology

    Species Description. The northern Mexican gartersnake ranges in 
color from olive to olive-brown or olive-gray with three stripes that 
run the length of the body, the middle of which darkens towards the 
tail. It may occur with other native gartersnake species and can be 
difficult for people without herpetological expertise to identify. The 
snake may reach a maximum known length of 44 inches (in) [(112 
centimeters (cm)]. The pale yellow to light-tan lateral stripes 
distinguish the northern Mexican gartersnake from other sympatric (co-
occurring) gartersnake species because a portion of the lateral stripe 
is found on the fourth scale row, while it is confined to lower scale 
rows for other species. Paired black spots extend along the olive 
dorsolateral fields (region adjacent to the top of the snake's back) 
and the olive-gray ventrolateral fields (region adjacent to the area of 
the snake's body in contact with the ground). A more detailed species 
description can be found in our 2006 12-month finding for this species 
(71 FR 56227), or by reviewing Rosen and Schwalbe (1988, p.4), Rossman 
et al. (1996, pp. 171-172), or Manjarrez and Garcia (1993, pp. 1-5).
    Taxonomy. The northern Mexican gartersnake is a member of the 
family Colubridae and subfamily Natricinae (harmless live-bearing 
snakes) (Lawson et al. 2005, p. 596). The taxonomy of the genus 
Thamnophis has a complex history, partly because many of the species 
are similar in appearance and scutelation (arrangement of scales), but 
also because many of the early museum specimens were in such poor and 
faded condition that it was difficult to study them (Conant 2003, p. 
6).
    In recent history and prior to 2003, Thamnophis eques was 
considered to have three subspecies, T. e. eques, T. e. megalops, and 
T. e. virgatenuis (Rossman et al. 1996, p. 175). In 2003, an additional 
seven new subspecies were identified under T. eques: (1) T. e. 
cuitzeoensis; (2) T. e. patzcuaroensis; (3) T. e. inspiratus; (4) T. e. 
obscurus; (5) T. e. diluvialis; (6) T. e. carmenensis; and (7) T. e. 
scotti (Conant 2003, p. 3). Common names were not provided, so in this 
finding, we use the scientific name for all subspecies of Mexican 
gartersnake other than the northern Mexican gartersnake. These seven 
new subspecies were described based on morphological differences in 
coloration and pattern; have highly restricted distributions; and occur 
in isolated wetland habitats within the mountainous Transvolcanic Belt 
region of southern Mexico, which contains the highest elevations in the 
country (Conant 2003, pp. 7-8). There are no known challenges within 
the scientific literature of the validity of current taxonomy of any of 
the 10 subspecies of T. eques. A more detailed description of the 
taxonomy of the northern Mexican gartersnake is found in our September 
26, 2006 12-month finding for this species (71 FR 56227). Additional 
information regarding this species' taxonomy can be found in De Queiroz 
et al. (2002, P. 323), De Queiroz and Lawson (1994, p. 217), Rossman et 
al. (1996, pp. xvii-xviii, pp. 171-175), Rosen and Schwalbe (1988, pp. 
2-3), Liner (1994, p. 107), and Crother (2008, p. 63).
    On many occasions throughout this finding, we discuss the status of 
and threats to several prey species of the northern Mexican 
gartersnake, including anuran (frog and toad) species of the genera 
historically known as Rana and Bufo (true frogs and true toads, 
respectively). Frost et al. (2006, pp. 9-11) proposed several taxonomic 
name changes, including many species under the genus Rana to 
Lithobates, and many species under the genus Bufo to Anaxyrus. Crother 
(2008, pp. 2-12), Committee Chair for the Standard English and 
Scientific Names Committee, adopted these scientific name changes. 
However, these taxonomic revisions have not escaped significant 
scrutiny in the scientific literature. Weins (2007, pp. 55-56) 
criticized the methodologies and analysis of Frost et al. (2006, pp. 9-
11). Subsequently, Frost et al. (2008, pp. 385-395) rebutted these 
criticisms. Throughout this finding, we continue to use the genera Rana 
and Bufo to maintain taxonomic familiarity among the interested 
parties, retain consistency in the Federal Register with respect to 
notices regarding the northern Mexican gartersnake, and allow ample 
opportunity for peer review and deliberation in the scientific 
community with respect to the findings of Frost et al. (2006, pp. 9-
11).
    Habitat. Throughout its rangewide distribution, the northern 
Mexican gartersnake occurs at elevations from 130 to 8,497 feet (ft) 
(40 to 2,590 meters (m)) (Rossman et al. 1996, p. 172). The northern 
Mexican gartersnake is a riparian obligate (restricted to riparian 
areas when not engaged in dispersal behavior) and occurs chiefly in the 
following general habitat types: (1) Source-area wetlands (e.g., 
cienegas (mid-elevation wetlands with highly organic, reducing (basic 
or alkaline) soils), stock tanks (small earthen impoundment), etc.); 
(2) large-river riparian woodlands and forests; and (3) streamside 
gallery forests (as defined by well-developed broadleaf deciduous 
riparian forests with limited, if any, herbaceous ground cover or dense 
grass) (Hendrickson and Minckley 1984, p. 131; Rosen and Schwalbe 1988, 
pp. 14-16; Arizona Game and Fish Department 2001). Additional 
information on the habitat requirements of the northern Mexican 
gartersnake within the United States and Mexico can be found in our 
2006 12-month finding for this species (71 FR 56227) and in Rosen and 
Schwalbe (1988, pp. 14-16), Rossman et al. (1996, p. 176), McCranie and 
Wilson (1987, pp. 11-17), and Cirett-Galan (1996, p. 156).
    Behavior, Prey Base, and Reproduction. The northern Mexican 
gartersnake is surface active at ambient temperatures ranging from 71 
degrees Fahrenheit ([deg]F) to 91 [deg]F (22 degrees Celsius ([deg]C) 
to 33 [deg]C) and forages along the banks of waterbodies. Rosen (1991, 
pp. 308-309) found that northern Mexican gartersnakes spent 
approximately 60 percent of their time

[[Page 71790]]

moving, 13 percent of their time basking on vegetation, 18 percent of 
their time basking on the ground, and 9 percent of their time under 
surface cover; body temperatures ranged from 24-33 [deg]C (75-91 
[deg]F) and averaged 28 [deg]C (82 [deg]F), which is lower than other, 
similar species with comparable habitat and prey preferences. Rosen 
(1991, p. 310) suggested that lower preferred body temperatures 
exhibited by northern Mexican gartersnakes may be due to both (1) their 
tendency to occupy cienega-like habitat where warm ambient temperatures 
are relatively unavailable; and, (2) their tendency to remain in dense 
cover.
    The northern Mexican gartersnake is an active predator and is 
believed to heavily depend upon a native prey base (Rosen and Schwalbe 
1988, pp. 18, 20). Northern Mexican gartersnakes forage generally along 
vegetated banklines, searching for prey in water and on land, using 
different strategies (Alfaro 2002, p. 209). Generally, its diet 
consists predominantly of amphibians and fishes, such as adult and 
larval native leopard frogs (e.g., lowland leopard frog (Rana 
yavapaiensis) and Chiricahua leopard frog (Rana chiricahuensis)), as 
well as juvenile and adult native fish species (e.g., Gila topminnow 
(Poeciliopsis occidentalis occidentalis), desert pupfish (Cyprinodon 
macularius), Gila chub (Gila intermedia), and roundtail chub (Gila 
robusta)) (Rosen and Schwalbe 1988, p. 18). Auxiliary prey items may 
also include young Woodhouse's toads (Bufo woodhousei), treefrogs 
(Family Hylidae), earthworms, deermice (Peromyscus spp.), lizards of 
the genera Aspidoscelis and Sceloporus, larval tiger salamanders 
(Ambystoma tigrinum), and leeches (Gregory et al. 1980, pp. 87, 90-92; 
Rosen and Schwalbe 1988, p. 20; Holm and Lowe 1995, pp. 30-31; 
Degenhardt et al. 1996, p. 318; Rossman et al. 1996, p. 176; Manjarrez 
1998). To a much lesser extent, this snake's diet may include nonnative 
species, including larval and juvenile bullfrogs, and mosquitofish 
(Gambusia affinis) (Holycross et al. 2006, p. 23). Venegas-Barrera and 
Manjarrez (2001, p. 187) reported the first observation of a snake in 
the natural diet of any species of Thamnophis after documenting the 
consumption by a Mexican gartersnake of a Mexican alpine blotched 
gartersnake (Thamnophis scalaris).
    Marc[iacute]as-Garc[iacute]a and Drummond (1988, pp. 129-134) 
sampled the stomach contents of Mexican gartersnakes and the prey 
populations at (ephemeral) Lake Tecocomulco, Hidalgo, Mexico. Field 
observations indicated with high statistical significance that larger 
snakes fed primarily upon aquatic vertebrates (fishes, frogs, and 
larval salamanders) and leeches, whereas smaller snakes fed primarily 
upon earthworms and leeches (Marc[iacute]as-Garc[iacute]a and Drummond 
1988, p. 131). Marc[iacute]as-Garc[iacute]a and Drummond (1988, p. 130) 
also found that parturition (birth) of neonatal T. eques tended to 
coincide with the annual peak density of annelids (earthworms and 
leeches). Positive correlations were also made with respect to capture 
rates (which are correlated with population size) of T. eques to lake 
levels and to prey scarcity; that is, when lake levels were low and/or 
prey species scarce, Mexican gartersnake capture rates declined 
(Marc[iacute]as-Garc[iacute]a and Drummond 1988, p. 132). This 
indicates the importance of available water and an adequate prey base 
to maintaining viable populations of Mexican gartersnakes. 
Marc[iacute]as-Garc[iacute]a and Drummond (1988, p. 133) found that 
while certain prey items were positively associated with size classes 
of snakes, the largest of specimens consume any prey available.
    Sexual maturity in northern Mexican gartersnakes occurs at 2 years 
of age in males and at 2 to 3 years of age in females (Rosen and 
Schwalbe 1988, pp. 16-17). Northern Mexican gartersnakes are 
ovoviviparous (eggs develop and hatch within the oviduct of the 
female). Mating occurs in April and May followed by the live birth of 
between 7 and 26 newborns (newly born individuals) (average is 13.6) in 
July and August (Rosen and Schwalbe 1988, p. 16). Unlike other 
gartersnake species, which typically breed annually, approximately half 
of the sexually mature females within a population of northern Mexican 
gartersnake reproduce in any one season (Rosen and Schwalbe 1988, p. 
17). This may have negative implications for the species' ability to 
rebound in isolated populations facing threats such as nonnative 
species, habitat modification or destruction, and other perturbations. 
Low birth rates will impede recovery of such populations by 
accentuating the effects of these threats.

Distribution

    Historical Distribution. Within the United States, the northern 
Mexican gartersnake historically occurred predominantly in Arizona at 
elevations ranging from 130 to 6,150 ft (40 to 1,875 m) in elevation. 
It was generally found where water was relatively permanent and 
supported suitable habitat. The northern Mexican gartersnake 
historically occurred in every county within Arizona, within several 
perennial or intermittent drainages and disassociated wetlands (Woodin 
1950, p. 40; Nickerson and Mays 1970, p. 503; Bradley 1986, p. 67; 
Rosen and Schwalbe 1988, Appendix I; 1995, p. 452; 1997, pp. 16-17; 
Holm and Lowe 1995, pp. 27-35; Sredl et al. 1995b, p. 2; 2000, p. 9; 
Rosen et al. 2001, Appendix I; Holycross et al. 2006, pp. 1-2, 15-51; 
Brennan and Holycross 2006, p. 123; Radke 2006; Rosen 2006; Holycross 
2006).
    Historically, the northern Mexican gartersnake had a limited 
distribution in New Mexico that consisted of scattered locations 
throughout the Gila and San Francisco headwater drainages in Grant and 
western Hidalgo Counties (Price 1980, p. 39; Fitzgerald 1986, Table 2; 
Degenhardt et al. 1996, p. 317; Holycross et al. 2006, pp. 1-2).
    One record for the northern Mexican gartersnake exists for the 
State of Nevada, opposite Fort Mohave, in Clark County along the shore 
of the Colorado River (De Queiroz and Smith 1996, p. 155). The species 
may have occurred historically in the lower Colorado River region of 
California, although we were unable to verify any museum records for 
California. Any populations of northern Mexican gartersnakes that may 
have historically occurred in either Nevada or California likely 
pertained directly to the Colorado River and are extirpated.
    Within Mexico, northern Mexican gartersnakes historically occurred 
within the Sierra Madre Occidental and the Mexican Plateau in the 
Mexican states of Sonora, Chihuahua, Durango, Coahila, Zacatecas, 
Guanajuato, Nayarit, Hidalgo, Jalisco, San Luis Potos[iacute], 
Aguascalientes, Tlaxacala, Puebla, M[eacute]xico, Veracruz, and 
Quer[eacute]taro, comprising approximately 85 percent of the total 
rangewide distribution of the species (Conant 1963, p. 473; 1974, pp. 
469-470; Van Devender and Lowe 1977, p. 47; McCranie and Wilson 1987, 
p. 15; Rossman et al. 1996, p. 173; Lemos-Espinal et al. 2004, p. 83).
    Status in the United States. Variability in survey design and 
effort makes it difficult to compare population trends among sites and 
between sampling periods. Thus, for each of the sites considered in our 
analysis, we have attempted to translate and quantify search and 
capture efforts into comparable units (i.e., person-search hours and 
trap-hours) and have cautiously interpreted those results. Given the 
data provided, it is not possible to determine population densities at 
the sites.
    A detailed status of the northern Mexico gartersnake in the United 
States and Mexico can be found in our 2006 12-month finding (71 FR 
56227) and in Holycross et al. (2006, p. 12); Rosen and Schwalbe (1988, 
Appendix 1); Rosen et

[[Page 71791]]

al. (2001, pp. 21-22, Appendix 1); d'Orgeix (2008); Holm and Lowe 
(1995, pp. 27-35). Subsequent to our 2006 12-month finding, we have 
obtained and analyzed additional information pertinent to the status of 
the northern Mexico gartersnake and present it below.
    Scotia Canyon was the last area intensively resurveyed by Rosen et 
al. (2001, pp. 15-16). In comparing capture rates from Holm and Lowe 
(1995, pp. 27-35), northern Mexican gartersnake populations in this 
area appear to have declined from 1980-1982, to low capture rates in 
1993, and even lower capture rates in 2000 (Boyarski 2008c, p. 1). In 
2008, a multi-party effort was initiated within Scotia Canyon, 
including the Peterson Ranch Pond and vicinity, to eradicate bullfrogs 
as well as record observations of Chiricahua leopard frogs or northern 
Mexican gartersnakes (Frederick 2008, 2008b). These efforts occurred in 
the same area investigated by Holm and Lowe (1995, pp. 27-35) and Rosen 
et al. (2001, pp. 15-16). After many surveys of herpetofauna (reptiles 
and amphibians) in this area to identify the presence of bullfrogs for 
eradication, a single, large adult northern Mexican gartersnake was 
observed, the first in over 8 years of informal surveys at this site 
(Frederick 2008b), which is frequently visited by biologists. This 
observation suggests that the species continues to occur in the upper 
Scotia Canyon area, but, given the extensive survey effort, it occurs 
in exceptionally low densities and no longer represents a stable 
population because of problems with reproduction and survivorship that 
exist with populations comprised of very low numbers of individuals.
    A significant amount of survey effort for northern Mexican 
gartersnakes was conducted at the Las Cienegas National Conservation 
Area (Cienega Creek and Empire Cienega) from 2002-2008. During the 2002 
and 2003 field seasons, Rosen and Caldwell (2004, pp. 1-52) conducted 
an in-depth assessment of the riparian herpetofaunal community of this 
area and in 11,784 trap-hours captured by hand and trap, 29 northern 
Mexican gartersnakes that were marked and released. Twenty-one northern 
Mexican gartersnakes were trapped, which equates to 561 trap-hours per 
snake. In 2004, Rosen and Caldwell (2004, p. 21) considered the species 
to be ``widely distributed, though perhaps reduced in abundance'' in 
this area.
    In 2007 and 2008, significant effort to collect northern Mexican 
gartersnakes was given to this same area using similar techniques as 
Rosen and Caldwell (2004) (Gartersnake Conservation Working Group 
(GCWG) 2008, pp. 1-10). Servoss et al. (2007, p. 4) captured one 
juvenile northern Mexican gartersnake by hand after 27 person search-
hours and 1,000 trap-hours of effort.
    Due to limited success in collecting the species in 2007, in 2008, 
the Arizona Game and Fish Department contracted with a recognized 
reptile and amphibian researcher familiar with the area to collect 
specimens for captive propagation (GCWG 2008, pp. 1-10). The 
herpetologist trapped a single juvenile northern Mexican gartersnake in 
3,612 trap-hours and 104 person search-hours of effort (Caldwell 2008a, 
2008b).
    The wildlife biologist for the Bureau of Land Management (BLM) 
Tucson Field Office (who has conducted fish sampling at the Las 
Cienegas National Conservation Area since 1998) expressed concerns for 
the apparent population decline of northern Mexican gartersnakes in 
this area. Several fish sampling techniques he employs are also used 
specifically to sample aquatic snake species such as the northern 
Mexican gartersnake. Simms (2008) stated that seining and hoop netting 
at 40 locations, as well as visual surveys of this area performed in 
2008, have yielded no observations of Mexican gartersnakes.
    The data from 2007 and 2008 confirm that this formerly stable 
population at the Las Cienegas National Conservation Area is 
experiencing significant declines, may no longer be viable, and could 
become extirpated in the near-term. In 2007 and 2008, more than 2,300 
trap-hours were required per snake captured (Caldwell 2008a, 2008b; 
Servoss et al. 2007, p. 1-12), compared with Rosen and Caldwell's 
(2004, p. 21 Table 2) capture rates of 561 trap-hours per snake in 2002 
and 2003. This is a more than four-fold increase in the effort needed 
to capture northern Mexican gartersnakes.
    The recently documented population of northern Mexican gartersnakes 
within Tonto Creek is the only known population that remains from the 
Salt River Basin (the status of the species in the basin on the White 
Mountain Apache and San Carlos Apache reservations remains unknown). 
Wallace et al. (2008, pp. 243-244) documented the first record of 
northern Mexican gartersnakes from the Tonto Creek watershed in Gila 
County, from a specimen that was observed in the road (killed by a 
vehicle) on State Route 188 in 1995. Seventeen individual northern 
Mexican gartersnakes were subsequently captured in Tonto Creek with 
20,444 trap-hours of effort (1,202 trap-hours per snake) in 2004 and 
2005 (Holycross et al. 2006, pp. 41-44; Wallace et al. 2008, pp. 243-
244). Wallace et al. (2008, pp. 243-244) suggest northern Mexican 
gartersnakes in Tonto Creek persist in low densities and raise the 
possibility that recruitment (the process by which individuals within a 
population achieve reproductive maturity) may be in decline because 
only adult and newborn specimens were captured, with no intermediate 
age classes observed.
    The population of northern Mexican gartersnakes along the Verde 
River within the Verde Valley of Yavapai County is presumed to remain 
as a low-density population. Approximately 15 individuals, including 
agency personnel and private citizens, surveyed the Verde River within 
the Verde Valley (including Dead Horse Ranch State Park) for the 
purpose of collecting 5 Mexican gartersnakes for captive propagation in 
2007 (GCWG 2007, p. 2). Approximately 120 person-search hours resulted 
in no observations of northern Mexican gartersnakes (GCWG 2007, p. 2). 
Haney et al. (2008, p. 61) declared the northern Mexican gartersnake 
nearly lost from the Verde River.
    A population of northern Mexican gartersnakes that remains at the 
Arizona Game and Fish Department's Page Springs and Bubbling Ponds fish 
hatcheries (hatcheries), located adjacent to Oak Creek, upstream of its 
confluence with the Verde River, represents the highest density 
population in Arizona and potentially the last remaining viable 
population in the United States. Boyarski (2008b, pp. 1-10) summarizes 
the first (2007) field season of a northern Mexican gartersnake 
monitoring project at the hatcheries, which had the objective of 
establishing the baseline population demographics from which to launch 
future investigations (Boyarski 2008b, p. 4). Although several capture 
techniques were employed, trapping was the most effective by far. In 
total, 52 individual northern Mexican gartersnakes were captured in 
2007; 42 from Bubbling Ponds, 8 from Page Springs, and 2 from the 
adjacent Oak Creek (Boyarski 2008b, p. 5). In total, 19,457 trap-hours 
captured 56 northern Mexican gartersnakes (including 7 recaptures), 
which equates to 347 trap-hours per capture (Boyarski 2008b, p. 6). As 
this was the first year to acquire population data for northern Mexican 
gartersnakes within the hatcheries, population trends at these sites 
cannot be determined. However, hatchery personnel stated that northern 
Mexican gartersnakes are not observed as frequently and do not appear 
to be as common as they once were at these sites

[[Page 71792]]

(Boyarski 2008b, p. 8). While not associated with a scientific study, 
this statement by hatchery personnel, who spend most of their time in 
the immediate vicinity of occupied habitat, is of special concern 
because it illustrates the potential that long-term declines may have 
been occurring at the hatchery although potential declines can not be 
quantified.
    Sonoita Creek in Santa Cruz County in southern Arizona was a 
historical location for northern Mexican gartersnakes. Turner (2006, 
pp. 1-21) found no northern Mexican gartersnakes in a herpetological 
inventory conducted from April through September 2006, in the Sonoita 
Creek State Natural Area. The last record of a northern Mexican 
gartersnake in this area was in 1974 and the subspecies was not found 
during Turner's 204-person-search-hour, 5,472-trap-hour survey effort 
(Turner 2006, pp. 3, 9). Crayfish, bullfrogs, and nonnative fish were 
observed by Turner (2006, p. 10) throughout the riparian area of the 
study area, as was evidence of improper livestock grazing.
    In our 2006 12-month finding for this species, we specified that 
the last known observation of the northern Mexican gartersnake in New 
Mexico occurred in 1994 on private land (Painter 2000, p. 36, Painter 
2005). In 2007, we became aware of a single photo-vouchered record of a 
northern Mexican gartersnake in New Mexico. The specimen was discovered 
and photo-vouchered in August 2002, observed in a debris pile along the 
Gila River off Highway 180 in Grant County, New Mexico (Hill 2007). 
Subsequent searches for northern Mexican gartersnakes were conducted in 
the same vicinity in 2006 and 2007, but no individuals were observed 
(Hill 2007). In our 2006 finding (71 FR 56227), we considered the 
northern Mexican gartersnake as extirpated from New Mexico. In 
consideration of: (1) A single observation of the species in New Mexico 
within the last 14 years that occurred in 2002; (2) 2 years of survey 
effort in 2006 and 2007 within the Gila River in the area of the 2002 
observation by Hill (2007); and (3) additional survey effort of 
historical habitat for the species in New Mexico in 2007, we consider 
the status of the northern Mexican gartersnake in the Gila River at the 
Highway 180 crossing in New Mexico as unknown at this time (Painter 
2008; Cotton 2008; Kindscher In Prep., pp. 1-26). All other historical 
locations of the northern Mexican gartersnake in New Mexico are 
considered extirpated (Painter 2005).
    General concerns within the scientific community exist for age 
class structure within northern Mexican gartersnake populations that 
have been affected by nonnative species. It is widely believed that 
recruitment of northern Mexican gartersnakes may be significantly 
impeded by nonnative predation on the neonate and juvenile age classes. 
Individuals that survive past these age classes are likely to have 
increased survivorship, in part by foraging on the nonnative species 
that preyed upon them during their younger age classes. These 
population-level observations have been made in several populations 
including Scotia Canyon (Holm and Lowe 1995, p. 34), Tonto Creek 
(Wallace et al. 2008, pp. 243-244), and the San Bernardino National 
Wildlife Refuge (Rosen and Schwalbe 1988, p. 18).
    Our analysis of the best available data on the status of the 
northern Mexican gartersnake distribution in the United States 
indicates that its distribution has been significantly reduced, and it 
is likely extirpated from a large portion of its historical 
distribution within the United States. We define a population as 
``likely extirpated'' when there have been no northern Mexican 
gartersnakes reported for a decade or longer at a site within the 
historical distribution of the species, despite survey efforts, and 
there is no expectation of natural recovery at the site due to the 
presence of known or strongly suspected causes of extirpation. The 
perennial or intermittent stream reaches and disassociated wetlands 
(i.e., stock tanks, ponds, cienegas, etc.) where the northern Mexican 
gartersnake has likely been extirpated in Arizona include: (1) The Gila 
River; (2) the Lower Colorado River from Davis Dam to the International 
Border; (3) the San Pedro River; (4) the Santa Cruz River downstream 
from the International Border at Nogales; (5) the Salt River; (6) the 
Rio San Bernardino from International Border to headwaters at Astin 
Spring (San Bernardino National Wildlife Refuge); (7) the Agua Fria 
River; (8) the Verde River upstream of Clarkdale; (9) the Verde River 
from the confluence with Fossil Creek downstream to its confluence with 
the Salt River; (10) Tanque Verde Creek in Tucson; (11) Rillito Creek 
in Tucson; (12) Agua Caliente Spring in Tucson; (13) Potrero Canyon/
Springs; (14) Babocamari Cienega; (15) Barchas Ranch, Huachuca Mountain 
bajada; (16) Parker Canyon Lake and tributaries in the Canelo Hills; 
and (17) Oak Creek at Midgley Bridge (Rosen and Schwalbe 1988, pp. 25-
26, Appendix I; 1997, pp. 16-17; Rosen et al. 2001, Appendix I; Brennan 
and Holycross 2006, p. 123; Holycross 2006; Holycross et al. 2006, pp. 
15-51, 66; Radke 2006; Rosen 2006).
    In New Mexico, the following historical populations are considered 
extirpated: (1) Mule Creek; (2) the Gila River, 5 miles (mi) (8 
kilometers (km)) east of Virden; (3) Spring Canyon; (4) the West Fork 
Gila River at Cliff Dwellings National Monument; (5) the Tularosa River 
at its confluence with the San Francisco River; (6) the San Francisco 
River at Tub Spring Canyon; (7) Little Creek at Highway 15; (8) the 
Middle Box of Gila River at Ira Ridge; (9) Turkey Creek; (10) Negrito 
Creek; and (11) the Rio Mimbres (Fitzgerald 1986, Table 2; Painter 
2005, 2006; 2008; Cotton 2008; Kindscher In Prep., pp. 1-26).
    Conversely, our review of the best available information indicates 
the northern Mexican gartersnake likely occurs in a fraction of its 
former range in Arizona. We define populations as ``likely occurring'' 
when the species is expected to reliably occur in appropriate habitat 
as supported by recent museum records and/or recent (i.e., less than 10 
years) reliable observations. The perennial or intermittent stream 
reaches and disassociated wetlands where we conclude northern Mexican 
gartersnakes remain include: (1) The Santa Cruz River/Lower San Rafael 
Valley (headwaters downstream to the International Border); (2) the 
Verde River from the confluence with Fossil Creek upstream to 
Clarkdale; (3) Oak Creek at Page Springs; (4) Tonto Creek from the 
mouth of Houston Creek downstream to Roosevelt Lake; (5) Cienega Creek 
from the headwaters downstream to the ``Narrows'' just downstream of 
Apache Canyon; (6) Pantano Wash (Cienega Creek) from Pantano downstream 
to Vail; (7) Appleton-Whittell Research Ranch and vicinity near Elgin; 
and (8) Red Rock Canyon east of Patagonia (Rosen et al. 2001, Appendix 
I; Caldwell 2005; Brennan and Holycross 2006, p. 123; Holycross 2006; 
Holycross et al. 2006, pp. 15-51, 66; Rosen 2006; Jones 2008a).
    The current status of the northern Mexican gartersnake is unknown 
in several areas within Arizona and New Mexico where the species is 
known to have historically occurred. We base this determination 
primarily on historical museum records for locations where survey 
access is restricted, survey data are unavailable or insufficient, and/
or current threats could preclude occupancy. The perennial or 
intermittent stream reaches and disassociated wetlands where the status 
of the northern Mexican gartersnake remains uncertain include: (1) The 
downstream portion of the Black River drainage from the Paddy Creek

[[Page 71793]]

confluence; (2) the downstream portion of the White River drainage from 
the confluence of the East and North forks; (3) Big Bonito Creek; (4) 
Lake O'Woods near Lakeside; (5) Spring Creek above the confluence with 
Oak Creek; (6) Bog Hole Wildlife Area; (7) Upper 13 Tank, Patagonia 
Mountain bajada; (8) Babocamari River; (9) Upper Scotia Canyon in the 
Huachuca Mountains; (10) Arivaca Cienega; and, (11) Gila River at 
Highway 180 (in New Mexico) (Rosen and Schwalbe 1988, Appendix I; Rosen 
et al. 2001, Appendix I; Brennan and Holycross 2006, p. 123; Holycross 
2006; Holycross et al. 2006, pp. 15-51; Rosen 2006).
    In summary, based upon our analysis of the best available 
scientific and commercial data, we conclude that the northern Mexican 
gartersnake has been extirpated from approximately 90 percent of its 
historical distribution in the United States.
    Status in Mexico. Determining the status and current distribution 
of the northern Mexican gartersnake in Mexico is difficult because of 
the lack of large-scale surveys, research, and other pertinent 
information. We can determine that there have been important large-
scale losses of northern Mexican gartersnake habitat, and that, at 
least locally, northern Mexican gartersnake populations have been 
extirpated or are declining. We relied, in part, on information that 
addresses the status of both riparian and aquatic biological 
communities that are habitat for the northern Mexican gartersnake and 
the status of native freshwater fish species that are documented prey 
species for the northern Mexican gartersnake from areas within its 
historical distribution in Mexico. From the status of those communities 
or fish species, we inferred a similar status for the northern Mexican 
gartersnake as we have no reason to conclude these particular predator-
prey relationships respond any differently to biological community-
level perturbations in Mexico as has been observed reliably in the 
United States. See Factors A and C for analysis of threats to the 
habitat and prey base.
    A large number of springs have dried up in several Mexican states 
within the distribution of the northern Mexican gartersnake, 
particularly from the years 1974-1994 in states including Chihuahua, 
Durango, Coahila, and San Luis Potos[iacute] (Contreras Balderas and 
Lozano 1994, p. 381). Because this has eliminated the habitat and 
aquatic prey base of the snake, we conclude that the northern Mexican 
gartersnake has also been lost from these sites. Contreras Balderas and 
Lozano (1994, p. 381) stated that several streams and rivers throughout 
Mexico and within the distribution of the northern Mexican gartersnake 
have also dried up or become intermittent due to overuse of surface and 
groundwater supplies. Ramirez Bautista and Arizmendi (2004, p. 3) 
stated that the principal threats to northern Mexican gartersnake 
habitat in Mexico include the drying of wetlands. Because this has 
decreased the amount of habitat and the aquatic prey base of the snake, 
we conclude that the northern Mexican gartersnake has likely declined 
at these sites.
    Burger (2008) provides a preliminary data set of survey effort for 
Mexican gartersnakes (Thamnophis eques), southern Durango spotted 
gartersnakes (T. nigronuchalis), and narrow-headed gartersnakes (T. 
rufipunctatus) from the United States and Mexico through 2007 (T. 
nigronuchalis only occurs in Mexico). The Burger (2008) data set 
provides information from surveys of 17 stream systems in the Mexican 
states of Durango and southern Chihuahua along the Sierra Madre 
Occidental during June 2007. Mexican gartersnakes were observed at 5 of 
the 17 sites visited; however, specimens were not identified to 
subspecies, and some sites visited may not have been within the 
historical distribution of the northern Mexican gartersnake. 
Individuals observed from locations in southern Durango were likely T. 
e. virgatenuis, rather than the northern Mexican gartersnake. This 
sampling effort in Mexico geographically constitutes a small portion of 
the range of the northern Mexican gartersnake in that country, but it 
provides limited regional insight into the species' status. Population 
trends at locations visited cannot be assessed because these sites have 
only been visited once.
    A research biologist with the Universidad Autonoma del Estado de 
M[eacute]xico, who has been doing field research on Mexican 
gartersnakes in central Mexico (within the distribution of northern 
Mexican gartersnakes) for approximately two decades, has documented the 
decline or disappearance of populations from drying of water bodies, 
water contamination, and other human impacts where, 20 years ago, the 
species was abundant (Manjarrez 2008).
    Determining the status of the northern Mexican gartersnake in 
Mexico is hampered by the lack of large-scale surveys, research, and 
other pertinent information for that country. We can determine that 
there have been important large-scale losses of northern Mexican 
gartersnake habitat, including surface waters such as rivers, streams, 
wetlands, and springs, that certainly have affected gartersnake 
populations. We can also determine that, where local surveys have been 
conducted, northern Mexican gartersnakes have been extirpated or are 
declining (Manjarrez 2008).

Summary of Factors Affecting the Northern Mexican Gartersnake

    Section 4 of the Act (16 U.S.C. 1533), and implementing regulations 
at 50 CFR 424, set forth procedures for adding species to the Federal 
Lists of Endangered and Threatened Wildlife and Plants. Under section 
4(a)(1) of the Act, we may list a species on the basis of any of five 
factors, as follows: (A) The present or threatened destruction, 
modification, or curtailment of its habitat or range; (B) 
overutilization for commercial, recreational, scientific, or 
educational purposes; (C) disease or predation; (D) the inadequacy of 
existing regulatory mechanisms; or (E) other natural or manmade factors 
affecting its continued existence. In making this finding, information 
regarding the status of, and threats to, the northern Mexican 
gartersnake in relation to the five factors provided in section 4(a)(1) 
of the Act is discussed below and summarized in Table 1 below.
    Table 1--Summary of northern Mexican gartersnake status and threats 
by population in the United States. (Note: ``Extirpated'' means that 
there have been no northern Mexican gartersnakes reported for a decade 
or longer at a site within the historical distribution of the species, 
despite survey efforts, and there is no expectation of natural recovery 
at the site due to the presence of known or strongly suspected causes 
of extirpation. ``Extant'' means areas where the species is expected to 
reliably occur in appropriate habitat as supported by museum records or 
recent, reliable observations. ``Unknown'' means areas where the 
species is known to have occurred based on museum records (mostly 
historical) but access is restricted, or survey data is unavailable or 
insufficient, or where threats could preclude occupancy.)

[[Page 71794]]



----------------------------------------------------------------------------------------------------------------
         Population locality                Current status           Regional historical or current threats
----------------------------------------------------------------------------------------------------------------
Gila River (outside of Highway 180     Extirpated.............  Factor A: Improper grazing, recreation,
 crossing) (Arizona, New Mexico).                                development, groundwater pumping, water
                                                                 diversions, channelization, dewatering, road
                                                                 construction/use, wildfire, intentional harm,
                                                                 dams.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Gila and San Francisco Headwaters      Extirpated.............  Factor A: Improper grazing, recreation.
 (New Mexico).
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Lower Colorado River from Davis Dam    Extirpated.............  Factor A: Recreation, development, road
 to International Border (Arizona).                              construction and use, borderland security and
                                                                 undocumented immigration, intentional harm,
                                                                 dams.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
San Pedro River in United States       Extirpated.............  Factor A: Improper grazing, groundwater pumping,
 (Arizona).                                                      road construction and use, borderland security
                                                                 and undocumented immigration, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Santa Cruz River downstream of the     Extirpated.............  Factor A: Improper grazing, development,
 Nogales area of the International                               groundwater pumping, water diversions,
 Border (Arizona).                                               channelization, road construction and use,
                                                                 borderland security and undocumented
                                                                 immigration, intentional harm, contaminants.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Salt River (Arizona).................  Extirpated.............  Factor A: Improper grazing, recreation,
                                                                 development, water diversions, wildfire,
                                                                 channelization, road construction/use,
                                                                 intentional harm, dams.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Rio San Bernardino from International  Extirpated.............  Factor A: Borderland security and undocumented
 Border to headwaters at Astin Spring                            immigration, intentional harm.
 (San Bernardino National Wildlife                              Factor C: Nonnative species, prey base
 Refuge, Arizona).                                               reduction.
                                                                Factor E: Competition with Marcy's checkered
                                                                 gartersnake.
Agua Fria River (Arizona)............  Extirpated.............  Factor A: Improper grazing, development,
                                                                 recreation, dams, road construction and use,
                                                                 wildfire, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Verde River upstream of Clarkdale      Extirpated.............  Factor A: Improper grazing, recreation,
 (Arizona).                                                      development, groundwater pumping, water
                                                                 diversions, channelization, road construction
                                                                 and use, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Verde River from the confluence with   Extirpated.............  Factor A: Improper grazing, recreation,
 the Salt upstream to Fossil Creek                               groundwater pumping, water diversions,
 (Arizona).                                                      channelization, road construction and use,
                                                                 wildfire, development, intentional harm, dams.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Potrero Canyon/Springs (Arizona).....  Extirpated.............  Factor A: Improper grazing.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Tanque Verde Creek in Tucson           Extirpated.............  Factor A: Improper grazing, recreation,
 (Arizona).                                                      development, groundwater pumping, road
                                                                 construction and use, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Rillito Creek in Tucson (Arizona)....  Extirpated.............  Factor A: Improper grazing, recreation,
                                                                 development, groundwater pumping, road
                                                                 construction and use, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Agua Caliente Spring in Tucson         Extirpated.............  Factor A: Improper grazing, recreation,
 (Arizona).                                                      development, groundwater pumping, road
                                                                 construction and use, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Babocamari Cienega (Arizona).........  Extirpated.............  Factor A: Improper grazing.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Barchas Ranch, Huachuca Mountain       Extirpated.............  Factor A: Improper grazing, borderland security
 bajada (Arizona).                                               and undocumented immigration, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Parker Canyon Lake and tributaries in  Extirpated.............  Factor A: Improper grazing, recreation, road
 the Canelo Hills (Arizona).                                     construction and use, borderland security and
                                                                 undocumented immigration, intentional harm,
                                                                 dams.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Oak Creek at Midgley Bridge (Arizona)  Extirpated.............  Factor A: Improper grazing, recreation,
                                                                 development, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Santa Cruz River/Lower San Rafael      Extant.................  Factor A: Improper grazing, borderland security
 Valley (headwaters downstream to                                and undocumented immigration, intentional harm.
 International Border) (Arizona).                               Factor C: Nonnative species, prey base
                                                                 reduction.
Verde River from the confluence with   Extant.................  Factor A: Improper grazing, recreation,
 Fossil Creek upstream to Clarkdale                              development, groundwater pumping, water
 (Arizona).                                                      diversions, channelization, road construction
                                                                 and use, intentional harm, dams.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Oak Creek at Page Springs (Arizona)..  Extant.................  Factor A: Development, construction, vehicle
                                                                 mortality.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction, domestic cat predation, parasites.
Tonto Creek from mouth of Houston      Extant.................  Factor A: Improper grazing, recreation,
 Creek downstream to Roosevelt Lake                              development, water diversions, channelization,
 (Arizona).                                                      road construction and use, wildfire,
                                                                 intentional harm, dams, flood control.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Cienega Creek from headwaters          Extant.................  Factor A: Improper grazing.
 downstream to the ``Narrows'' just                             Factor C: Nonnative species, prey base
 downstream of Apache Canyon                                     reduction.
 (Arizona).

[[Page 71795]]

 
Pantano Wash (Cienega Creek) from      Extant.................  Factor A: Improper grazing, development,
 Pantano downstream to Vail (Arizona).                           wildfire.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Appleton-Whittell Research Ranch and   Extant.................  Factor A: Improper grazing.
 vicinity near Elgin (Arizona).                                 Factor C: Nonnative species, prey base
                                                                 reduction.
Upper Scotia Canyon in the Huachuca    Unknown................  Factor A: Wildfire.
 Mountains (Arizona).
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Downstream portion of the Black River  Unknown................  Factor A: Improper grazing, recreation,
 drainage from the Paddy Creek                                   intentional harm.
 confluence (Arizona).                                          Factor C: Nonnative species, prey base
                                                                 reduction.
Downstream portion of the White River  Unknown................  Factor A: Improper grazing, recreation, road
 drainage from the confluence of the                             construction and use, intentional harm.
 East/North (Arizona).                                          Factor C: Nonnative species, prey base
                                                                 reduction.
Big Bonito Creek (Arizona)...........  Unknown................  Factor A: Improper grazing.
                                                                Factor C: Nonnative species, prey base
                                                                 reductions.
Lake O' Woods (Lakeside, Arizona)....  Unknown................  Factor A: recreation, development, road
                                                                 construction/use, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Spring Creek above confluence with     Unknown................  Factor A: Development.
 Oak Creek (Arizona).                                           Factor C: Nonnative species, prey base
                                                                 reduction.
Bog Hole Wildlife Area (Arizona).....  Unknown................  Factor C: Nonnative species, prey base
                                                                 reduction.
Upper 13 Tank, Patagonia Mountains     Unknown................  Factor A: Improper grazing.
 bajada (Arizona).
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Babocamari River (Arizona)...........  Unknown................  Factor A: Improper grazing.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Arivaca Cienega (Arizona)............  Unknown................  Factor A: Improper grazing, borderland security
                                                                 and undocumented immigration, intentional harm.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
Gila River at Highway 180 (New         Unknown................  Factor A: Improper grazing, recreation,
 Mexico).                                                        development, groundwater pumping, water
                                                                 diversions, channelization, dewatering, road
                                                                 construction/use, wildfire, intentional harm,
                                                                 dams.
                                                                Factor C: Nonnative species, prey base
                                                                 reduction.
----------------------------------------------------------------------------------------------------------------

References: For each of the population localities discussed in Table 1, 
a detailed textual discussion of the identified threats, including 
applicable reference citations, is found in subsequent sections of this 
finding related to each of the five listing factors. Site-specific 
information from locations in Mexico is limited and, therefore, 
locations in Mexico are not included in this table. Where available, 
the information from Mexico is presented and cited in our discussion of 
the five listing factors below.
    In the discussions of Factors A through E below, we describe the 
known factors that have contributed to the current status of the 
northern Mexican gartersnake. For populations within the United States, 
our analysis benefitted from the availability of specific research, 
monitoring, and other studies. The discussion of these factors that 
pertain to the status and threats to the northern Mexican gartersnake 
in Mexico are mainly regional, or statewide, in scope because, in many 
cases, there was limited specific information available. In some 
instances, we do include discussion on more refined geographic areas of 
Mexico when supported by the literature. It is important to understand, 
however, that many of the threats that affect the northern Mexican 
gartersnake in the United States are also likely present in Mexico, as 
further discussed below, despite the lack of formal documentation. 
Thus, we expect impacts to the habitat and the species to be similar in 
the United States and Mexico.
A. The Present or Threatened Destruction, Modification, or Curtailment 
of Its Habitat or Range
    Various threats that have affected and continue to affect riparian 
and aquatic communities that provide habitat for the northern Mexican 
garter snake include dams, water diversions, groundwater pumping, 
introduction of nonnative species (vertebrates, plants, and crayfish), 
woodcutting, recreation, mining, contaminants, urban and agricultural 
development, road construction, improper livestock grazing, wildfires, 
and undocumented immigration (Hendrickson and Minckley 1984, p. 161; 
Ohmart et al. 1988, p. 150; Bahre 1995, pp. 240-252; Medina 1990, p. 
351; Sullivan and Richardson 1993, pp. 35-42; Fleischner 1994, pp. 630-
631; Hadley and Sheridan 1995; Hale et al. 1995, pp. 138-140; DeBano 
and Neary 1996, pp. 73-75; Rinne and Neary 1996, p. 135; Stromberg et 
al. 1996, pp. 124-127; Girmendock and Young 1997, pp. 45-52; Rinne et 
al. 1998, pp. 7-11; Belsky et al. 1999, pp. 8-12; Esque and Schwalbe 
2002, pp. 165, 190; Hancock 2002, p. 765; Voeltz 2002, pp. 87-88; Webb 
and Leake 2005, pp. 305-308; Holycross et al. 2006, pp. 52-61; McKinnon 
2006a, 2006b, 2006c, 2006d, 2006e; Paradzick et al. 2006, pp. 88-93; 
Segee and Neeley 1996, Executive Summary, pp. 10-12, 21-23; Burger 
2008, USFS 2008; USFWS 2007, pp. 25, 35-39; Gila County Board of 
Supervisors 2008, pp. 1-2; Kimmel 2008; Trammell 2008; Sanchez 2008; 
Lyons and Navarro-Perez 1990, p. 37; Minckley et al. 2002, pp. 696; 
Nijhuis 2007, pp. 1-7; Ouren et al. 2007, pp. 16-22; Rorabaugh 2008, 
pp. 25-26). Threats to northern Mexican gartersnake habitat in Mexico 
include the intentional and unintentional introductions of nonnative 
species, improper livestock grazing, urbanization and development, 
water diversions and groundwater pumping, loss of vegetation cover and 
deforestation, erosion, and pollution, as well as impoundments and dams 
that have modified or destroyed riparian and aquatic communities within 
Mexico in areas where the species occurred historically (Conant 1974, 
p. 471; Lyons and Navarro-Perez 1990, p. 37; Contreras Balderas and 
Lozano 1994, p.

[[Page 71796]]

384; va Landa et al. 1997, p. 316; Jim[eacute]nez-Ruiz et al. 2002, p. 
458; Minckley et al. 2002, pp. 696; Miller et al. 2005, pp. 60-61; 
Abarca 2006; Burger 2008; Luja and Rodr[iacute]guez-Estrella 2008, pp. 
17-22; Rorabaugh 2008, pp. 25-26; Manjarrez 2008).
    Rorabaugh (2008, pp. 25-26) noted threats to northern Mexican 
gartersnakes and their native amphibian prey base in Sonora, which 
included disease, pollution, improper livestock grazing, conversion of 
land for agriculture, nonnative plant invasions, and logging. Ramirez 
Bautista and Arizmendi (2004, p. 3) stated that the principal threats 
to northern Mexican gartersnake habitat in Mexico include the drying of 
wetlands, improper livestock grazing, deforestation, wildfires, and 
urbanization. In addition, nonnative species, such as bullfrogs and 
sport and bait fish, have been introduced throughout Mexico and 
continue to disperse naturally, broadening their distributions (Conant 
1974, pp. 487-489; Miller et al. 2005, pp. 60-61; Luja and 
Rodr[iacute]guez-Estrella 2008, pp. 17-22).
    The activities outlined above for both the United States and Mexico 
and their effects on the northern Mexican gartersnake are discussed in 
further detail below. It is important to recognize that in most areas 
where northern Mexican gartersnakes historically or currently occur, 
two or more threats may be acting in combination in their influence on 
the suitability of those habitats or on the northern Mexican 
gartersnake itself. In our assessment of the status of these habitats, 
discussion of the role that nonnative species introductions have had on 
habitat suitability is critical. However, we provide that discussion 
under ``Factor C. Disease and Predation'' due to the intricate and 
complex relationship nonnative species have with respect to direct and 
indirect pressures applied to the northern Mexican gartersnake and to 
its native prey base.
Destruction and Modification of Riparian and Aquatic Biological 
Communities
    The modification and destruction of aquatic and riparian 
communities in the post-settlement arid southwestern United States is 
well documented (Medina 1990, p. 351; Sullivan and Richardson 1993, pp. 
35-42; Fleischner 1994, pp. 630-631; Stromberg et al. 1996, pp. 113, 
123-128; Girmendock and Young 1997, pp. 45-52; Belsky et al. 1999, pp. 
8-12; Webb and Leake 2005, pp. 305-310; Holycross et al. 2006, pp. 52-
61; Nijhuis 2007, pp. 1-7; Ouren et al. 2007, pp. 16-22). Several 
threats have been identified in the decline of many native riparian 
flora and fauna species through habitat modification and destruction, 
as well as nonnative species introductions. Researchers agree that the 
period from 1850 to 1940 marked the greatest loss and degradation of 
riparian and aquatic communities in Arizona, which were caused by 
anthropogenic (human-caused) land uses and the primary and secondary 
effects of those uses (Stromberg et al. 1996, p. 114; Webb and Leake 
2005, pp. 305-310). Many of these land activities continue today and 
are discussed in detail below. An estimated one-third of Arizona's pre-
settlement wetlands have dried or have been rendered ecologically 
dysfunctional (Yuhas 1996).
    Modification and Loss of Cienegas. Cienegas are particularly 
important habitat for the northern Mexican gartersnake and are 
considered ideal for the species (Rosen and Schwalbe 1988, p. 14). 
Hendrickson and Minckley (1984, p. 131) defined cienegas as ``mid-
elevation (3,281-6,562 ft (1,000-2000 m)) wetlands characterized by 
permanently saturated, highly organic, reducing [lowering of oxygen 
level] soils.'' Many of these unique communities of the southwestern 
United States, Arizona in particular, and Mexico have been lost in the 
past century to streambed modification, improper livestock grazing, 
woodcutting, artificial drainage structures, stream flow stabilization 
by upstream dams, channelization, and stream flow reduction from 
groundwater pumping and water diversions (Hendrickson and Minckley 
1984, p. 161). Stromberg et al. (1996, p. 114) state that cienegas were 
formerly extensive along streams of the Southwest; however, most were 
destroyed during the late 1800s, when groundwater tables declined 
several meters and stream channels became incised.
    Nonnative shrub species in the genus Tamarix, such as salt cedar, 
have been widely introduced throughout the western States and appear to 
thrive in regulated river systems (Stromberg and Chew 2002, pp. 210-
213). Tamarix invasions may result in habitat alteration from potential 
effects to water tables, changes to canopy and ground vegetation 
structures, and increased fire risk, which hasten the loss of native 
cottonwood and willow communities and affect the suitability of the 
vegetation component to northern Mexican gartersnake habitat (Stromberg 
and Chew 2002, pp. 211-212; USFWS 2002b, p. H-9).
    Many sub-basins, where cienegas have been severely modified or lost 
entirely, wholly or partially overlap the historical distribution of 
the northern Mexican gartersnake, including the San Simon, Sulphur 
Springs, San Pedro, and Santa Cruz valleys of southeastern and south-
central Arizona. The San Simon Valley in Arizona possessed several 
natural cienegas with luxuriant vegetation prior to 1885, and was used 
as a watering stop for pioneers, military, and surveying expeditions 
(Hendrickson and Minckley 1984, pp. 139-140). In the subsequent 
decades, the disappearance of grasses and commencement of severe 
erosion were the result of heavy grazing pressure by large herds of 
cattle, as well as the effects from wagon trails that paralleled 
arroyos, occasionally crossed them, and often required stream bank 
modification (Hendrickson and Minckley 1984, p. 140). Today, only the 
artificially maintained San Simon Cienega exists in this valley. 
Similar accounts of past conditions, adverse effects from historical 
anthropogenic activities, and subsequent reduction in the extent and 
quality of cienega habitats in the remaining valleys are also provided 
in Hendrickson and Minckley (1984, pp. 138-160).
    Urban and Rural Development. Development within and adjacent to 
riparian areas has proven to be a significant threat to riparian 
biological communities and their suitability for native species (Medina 
1990, p. 351). Riparian communities are sensitive to even low levels 
(less than 10 percent) of urban development within a watershed (Wheeler 
et al. 2005, p. 142). Development along or within proximity to riparian 
zones can alter the nature of stream flow dramatically, changing once-
perennial streams into ephemeral streams, which has direct consequences 
on the riparian community (Medina 1990, pp. 358-359) and, within 
occupied habitat, the northern Mexican gartersnake. Medina (1990, pp. 
358-359) concluded that perennial streams had greater tree densities in 
all diameter size classes of Alnus oblongifolius (Arizona alder) and 
Acer negundo (box elder) as compared to ephemeral reaches where small-
diameter trees were absent. Small-diameter trees assist the northern 
Mexican gartersnake by providing additional habitat complexity and 
cover needed to reduce predation risk and enhance the usefulness of 
areas for maintaining optimal body temperature.
    Obvious examples of the influence of urbanization and development 
can be observed within the areas of greater Tucson and Phoenix, 
Arizona, where impacts have modified riparian vegetation, structurally 
altered stream

[[Page 71797]]

channels, facilitated nonnative species introductions, and dewatered 
large reaches of formerly perennial rivers where the northern Mexican 
gartersnake historically occurred (Santa Cruz, Gila, and Salt rivers, 
respectively). Urbanization and development of these areas, along with 
the introduction of nonnative species, are largely responsible for the 
likely extirpation of the northern Mexican gartersnake from these 
areas.
    Urbanization on smaller scales can also impact habitat suitability 
and the prey base for the northern Mexican gartersnake. Regional 
development and subsequent land use changes, spurred by increasing 
populations, along lower Tonto Creek and within the Verde Valley where 
northern Mexican gartersnakes occur, continue to threaten this snake's 
habitat and affect the habitat's suitability for the northern Mexican 
gartersnake and its prey species (Girmendock and Young 1997, pp. 45-52; 
Voeltz 2002, pp. 58-59, 69-71; Paradzick et al. 2006, pp. 89-90). 
Holycross et al. (2006, pp. 53, 56) recently documented the damage and 
removal of northern Mexican gartersnake streamside habitat from 
development in the vicinity of Rock Springs along the Agua Fria River 
and also within the Verde Valley along the Verde River.
    Ongoing small-scale development projects within the Page Springs 
and Bubbling Ponds fish hatcheries along Oak Creek, upstream of its 
confluence with the Verde River, occur within potentially the most 
robust remaining population of northern Mexican gartersnakes in the 
United States (AGFD 1997a, pp. 1-13; 1997b, pp. 1-12). The Page Springs 
trout hatchery is an 82-acre (ac) (33-hectare (ha)) facility located 
within a semi-desert grassland vegetative community (AGFD 1997a, p. 3). 
It is the largest State-run hatchery and was renovated in 1993, 
resulting in construction-related impacts such as the removal of 
riparian vegetation and other earth-moving activities to occupied snake 
habitat (AGFD 1997a, p.1). Current and future management and 
maintenance of Page Springs include a variety of activities that would 
potentially affect occupied snake habitat, such as the maintenance of 
roads, buildings, fences, equipment, as well as development 
(residences, storage facilities, asphalt, resurfacing, etc.) and both 
human- and habitat-based enhancement projects (AGFD 1997a, p. 8). 
Implementation of such projects is expected to result in the damage or 
removal of habitat or potentially the contamination of habitat from the 
use of industrial products and chemicals. These projects may adversely 
affect the northern Mexican gartersnake directly through physical harm 
or injury or indirectly from effects to its habitat or prey base.
    The Bubbling Ponds hatchery, which raises nonnative and native fish 
(largemouth bass, smallmouth bass, and bluegill, Colorado River 
pikeminnow, razorback sucker), is located on Oak Creek, just north of 
the Page Springs hatchery, and comprises 2 parcels approximately 117 ac 
(47 ha) in size (AGFD 1997b, p. 2). The hatchery consists of 11 earthen 
ponds and 6 lined ponds totaling 10 surface acres (4 surface hectares), 
3 residential structures, and the hatchery building (AGFD 1997b, p. 2). 
Hatchery operations are confined to 17 of the 117 ac (7 of 47 ha) and 
have been modified extensively (AGFD 1997b, p. 4). The remaining 100 ac 
(40 ha) support riparian woodland and forest along Oak Creek (AGFD 
1997b, p. 4). Northern Mexican gartersnakes are presumed to occur 
throughout this property; using the earthen ponds for foraging on young 
bullfrogs, their tadpoles, and fish, and using areas near or adjacent 
to structures on the property. Current and future management and 
maintenance of Bubbling Ponds include a variety of activities that 
would potentially affect snake habitat, such as the maintenance of 
roads, buildings, fences, equipment, as well as development 
(residences, storage facilities, asphalt, resurfacing, etc.) and both 
human- and habitat-based enhancement projects (AGFD 1997b, pp. 8-9; 
Wilson and Company 1991, pp. 1-40; 1992, pp. 1-99). Implementation of 
such projects is expected to result in the damage or removal of habitat 
or potentially the contamination of habitat from the use of industrial 
products and chemicals. The small-scale development projects at these 
hatcheries may injure or kill northern Mexican gartersnakes or their 
prey base, and may also temporarily damage or remove occupied habitat. 
The Arizona Game and Fish Department is a long-standing partner in 
research and survey efforts related to the northern Mexican 
gartersnake, and there is an ongoing population study at the 
hatcheries. Adaptive management in relation to activities at the 
hatcheries, as informed by the population study, will help reduce the 
overall effects to gartersnakes and their habitat at the hatcheries.
    The effects of urban and rural development are expected to increase 
as human populations increase. Consumer interest in second home and/or 
retirement real estate investments has increased significantly in 
recent times within the southwestern United States. Medina (1990, p. 
351) points out that many real estate investors are looking for 
aesthetically scenic, mild climes to enjoy seasonally or year-round and 
hence choose to develop pre- or post-retirement properties that are 
within or adjacent to riparian areas due to their aesthetic appeal and 
available water, especially in the southwestern United States. Arizona 
increased its population by 394 percent from 1960 to 2000, and is 
second only to Nevada as the fastest growing State in terms of human 
population (Social Science Data Analysis Network (SSDAR) 2000, p.1). 
Over the same time period, population growth rates in Arizona counties 
where the northern Mexican gartersnake historically occurred or may 
still occur have varied by county but are no less remarkable, and all 
are increasing: Maricopa (463 percent); Pima (318 percent); Santa Cruz 
(355 percent); Cochise (214 percent); Yavapai (579 percent); Gila (199 
percent); Graham (238 percent); Apache (228 percent); Navajo (257 
percent); Yuma (346 percent); LaPaz (142 percent); and Mohave (2004 
percent) (SSDAR 2000).
    Population growth trends in Arizona, Maricopa County in particular, 
are expected to continue into the future. The Phoenix metropolitan 
area, founded in part due to its location at the junction of the Salt 
and Gila rivers, is a population center of 3.63 million people. The 
Phoenix metropolitan area is the sixth largest in the United States and 
resides in the fastest growing county in the United States since the 
2000 census (Arizona Republic 2006). Given the large amount of 
perennial habitat at the confluence of two large, flowing rivers that 
was historically present in this area prior to settlement, northern 
Mexican gartersnakes likely maintained dense populations in this region 
of Arizona. However, with the burgeoning population growth and 
associated urbanization and development that have occurred since, any 
remaining habitat for the northern Mexican gartersnake has been 
rendered unsuitable and the subspecies is now likely extirpated from 
this area and its recovery is unlikely.
    Massive growth predictions have been made for traditionally rural 
portions of Arizona. The populations of developing cities and towns of 
the Verde watershed are expected to more than double in the next 50 
years, which may pose exceptional threats to riparian and aquatic 
communities of the Verde Valley where northern Mexican gartersnakes 
occur (Girmendock and Young 1993, p. 47; American Rivers 2006; 
Paradzick et al. 2006, p. 89). Communities in Yavapai and Gila

[[Page 71798]]

counties such as the Prescott-Chino Valley, Strawberry, Pine, and 
Payson have all seen rapid population growth in recent years. For 
example, the population in the town of Chino Valley, at the headwaters 
of the Verde River, has grown by 22 percent between 2000 and 2004; Gila 
County, which includes reaches of the Salt, White, and Black rivers and 
Tonto Creek, grew by 20 percent between 2000 and 2003 (http://www.census.gov). The upper San Pedro River is also the location of 
rapid population growth in the Sierra Vista-Huachuca City-Tombstone-
Benson area (http://www.census.gov). All of these communities are near 
or within the vicinity of historical or current northern Mexican 
gartersnake populations.
    In Mexico, the magnitude and significance of adverse effects to 
riparian communities related to development lags somewhat behind that 
experienced in the United States due to slower population and economic 
growth, but it is reported that threats to riparian and aquatic 
communities that have been observed in Arizona are currently occurring 
with increasing significance in Mexico (Conant 1974, pp. 471, 487-489; 
Contreras Balderas and Lozano 1994, pp. 379-381; va Landa et al. 1997, 
p. 316; Miller et al. 2005, p. 60-61; Abarca 2006; Rosen 2006).
    Ortega-Huerta and Kral (2007, p. 1) found that land legislation 
within Mexico has changed considerably over recent years to integrate 
free market policies into local agricultural production methods that 
may result in the loss of land management practices that protect the 
natural environment. Community-based lands generally presented higher 
instance of habitat conservation in terms of natural vegetation, higher 
species aggregations, more evenly distributed cover types, and greater 
species richness (Ortega-Huerta and Kral 2007, p. 1). These 
correlations between land ownership and bird and mammal species 
richness can be generally extrapolated to other aspects of biotic 
communities, including the aquatic and semi-aquatic communities within 
areas. A shift away from traditional land management in Mexico presents 
threats to riparian and aquatic habitats occupied by the northern 
Mexican gartersnake.
    Collectively, development impacts of all types in Mexico are 
expected to continue as a result of Mexico's expanding role as an 
economical labor force for international manufacturing under the North 
American Free Trade Agreement (NAFTA) and the subsequent increase in 
population size, economic growth and development, and infrastructure. 
The threats to northern Mexican gartersnake habitat in riparian and 
aquatic communities in Mexico vary in their significance, based on 
geographical distribution of land management activities and urban 
centers, but are expected to continue into the future.
    Mexico's human population grew 700 percent from 1910 to 2000 
(Miller et al. 2005, p. 60). Mexico's population increased by 245 
percent from 1950 to 2002, and is projected to grow by another 28 
percent by 2025 (EarthTrends 2005). As of 1992, Mexico had the second 
highest gross domestic product in Latin America at 5.8 percent, 
following Brazil (DeGregorio 1992, p. 60). As a result of NAFTA, the 
number of maquiladoras (export assembly plants) is expected to increase 
by as many as 3,000 to 4,000 (Contreras Balderas and Lozano 1994, p. 
384). To accommodate Mexico's increasing human population, rural areas 
are largely devoted to food production based on traditional methods, 
which has led to serious losses in vegetative cover and soil erosion 
(va Landa et al. 1997, p. 316).
    Road Construction, Use, and Maintenance. Roads cover approximately 
1 percent of the land area in the United States, but negatively affect 
20 percent of the habitat and biota in the United States (Angermeier et 
al. 2004, p. 19). Roads pose unique threats to herpetofauna and 
specifically to species like the northern Mexican gartersnake, its prey 
base, and the habitat where it occurs through: (1) Fragmentation, 
modification, and destruction of habitat; (2) increase in genetic 
isolation; (3) alteration of movement patterns and behaviors; (4) 
facilitation of the spread of nonnative species via human vectors; (5) 
an increase in recreational access and the likelihood of subsequent, 
decentralized urbanization; (6) interference with or inhibition of 
reproduction; (7) contributions of pollutants to riparian and aquatic 
communities; and (8) population sinks (a factor resulting in 
unnaturally high death rates that exceed birth rates within a 
population) through direct mortality (Rosen and Lowe 1994, pp. 146-148; 
Waters 1995, p. 42; Carr and Fahrig 2001, pp. 1074-1076; Hels and 
Buchwald 2001, p. 331; Smith and Dodd 2003, pp. 134-138; Angermeier et 
al. 2004, pp. 19-24; Shine et al. 2004, pp. 9, 17-19; Andrews and 
Gibbons 2005, pp. 777-781; Wheeler et al. 2005, pp. 145, 148-149; Roe 
et al. 2006, p. 161).
    Construction and maintenance of roads and highways near riparian 
areas can be a source of sediment and pollutants (Waters 1995, p. 42; 
Wheeler et al. 2005, pp. 145, 148-149). Sediment can adversely affect 
fish populations used as prey by the northern Mexican gartersnake by 
(1) interfering with respiration; (2) reducing the effectiveness of 
fish's visually-based hunting behaviors; and (3) filling in 
interstitial spaces of the substrate, which reduces reproduction and 
foraging success of fish (Wheeler et al. 2005, p. 145). Excessive 
sediment also fills in intermittent pools required for amphibian prey 
reproduction and foraging. Fine sediment pollution in streams impacted 
by highway construction without the use of sediment control structures 
was 5 to 12 times greater than control streams (Wheeler et al. 2005, p. 
144). As stated above, sediment can lead to several effects in resident 
fish species used by northern Mexican gartersnakes as prey, which can 
ultimately cause increased direct mortality, reduced reproductive 
success, lower overall abundance of the northern Mexican gartersnake, 
lower species diversity of prey, and reductions in food base as 
documented by Wheeler et al. (2005, p. 145). The underwater foraging 
ability of northern Mexican gartersnakes is also directly compromised 
by excessive turbidity caused by sedimentation of water bodies, because 
this snake locates its prey visually.
    Metal contaminants, including iron, zinc, lead, cadmium, nickel, 
copper, and chromium, are associated with highway construction and use 
(Foreman and Alexander 1998, p. 220; Hopkins et al. 1999, p. 1260; 
Campbell et al. 2005, p. 241; Wheeler et al. 2005, pp. 146-149) and are 
bioaccumulative. A bioaccumulative substance increases in concentration 
in an organism or in the food chain over time. A mid- to higher-order 
predator, such as a gartersnake, may therefore accumulate these types 
of contaminants over time in their fatty tissues, which may lead to 
adverse health effects. Several studies have addressed the effects of 
bioaccumulative substances on watersnakes. We find these studies 
relevant because watersnakes and gartersnakes have very similar life 
histories and prey bases and, therefore, the effects from contamination 
of their habitat from bioaccumulative agents are expected to be 
similar. Campbell et al. (2005, pp. 241-243) found that metal 
concentrations accumulated in the northern watersnake (Nerodia sipedon) 
at levels six times that of their primary food item, the central 
stoneroller (fish) (Campostoma anomalum). Metals, in trace amounts, 
affect the structure and

[[Page 71799]]

function of the liver and kidneys of vertebrates and may also act as 
neurotoxins, affecting nervous system function (Rainwater et al. 2005, 
p. 670). Metals may also be sequestered in the skin of reptiles, but 
this effect is tempered somewhat by ecdysis (the regular shedding or 
molting of the skin) (Burger 1999, p. 212). Hopkins et al. (1999, p. 
1261) found that metals may even interfere with metabolic rates of 
banded watersnakes (Nerodia fasciata), altering the allocation of 
energy between maintenance and reproduction, reducing the efficiency of 
energy stores, and forcing individuals to forage more often, which 
increases activity costs (the energy expended in hunting, which affects 
the net nutritional intake of an organism) and predation risk.
    Snakes of all species are particularly vulnerable to mortality when 
they attempt to cross roads. Snakes are animals that derive heat from 
warm surfaces, which often compels them to slow down or even stop and 
rest on road surfaces that have been warmed by the sun as they attempt 
to cross (Rosen and Lowe 1994, p. 143). Gartersnakes are generally 
diurnal (active during daylight hours) and are often active when 
traffic densities are greatest (Rosen and Lowe 1994, p. 147). Mortality 
data have been collected at the Bubbling Ponds Hatchery since 2006. Of 
the eight dead specimens, half were struck by vehicles on roads 
adjacent to the hatchery ponds that are crossed by northern Mexican 
gartersnakes in traveling between ponds to forage (Boyarski 2008a). Van 
Devender and Lowe (1977, p. 47), however, observed several northern 
Mexican gartersnakes crossing the road at night after the commencement 
of the summer monsoon (rainy season), which highlights the seasonal 
variability in surface activity of this snake. Perhaps the most common 
factor in road mortality of snakes is the propensity for drivers to 
intentionally run over snakes, which generally make easy targets 
because they usually cross roads at a perpendicular angle (Klauber 
1956, p. 1026; Langley et al. 1989, p. 47; Shine et al. 2004, p. 11). 
This driving behavior is exacerbated by the general animosity that 
humans have toward snakes (Ernst and Zug 1996, p. 75; Green 1997 pp. 
285-286). In fact, Langley et al. (1989, p. 47) conducted an experiment 
on the propensity for drivers to hit reptiles on the road using turtle 
and snake models and found that many people have a greater desire to 
hit a snake on the road than any other animal; several drivers actually 
stopped and backed-over the snake mimic to ensure it was dead. Roe et 
al. (2006, p. 161) conclude that mortality rates due to roads are 
higher in vagile (mobile) species, such as gartersnakes (active 
hunters), than those of more sedentary species, which more commonly 
employ sit-and-wait foraging strategies. Roads that bisect wetland 
communities also act as mortality sinks in the dispersal or migratory 
movements of snakes (Roe et al. 2006, p. 161). The effect of road 
mortality of snakes becomes most significant in the case of small, 
highly fragmented populations where the chance removal of mature 
females from the population may appreciably degrade the viability of a 
population.
    Even lightly used roads may also lead to mortality of northern 
Mexican gartersnakes. For example, gravel roads that surround the 
hatchery ponds that are traveled by hatchery, research lab, and 
resident vehicles at the Bubbling Ponds fish hatchery have resulted in 
four documented northern Mexican gartersnake mortalities since 
mortality data began being collected in 2006 (Boyarski 2008a, pp. 1-4). 
These vehicle mortalities represent 50 percent of the mortalities 
documented at the hatcheries. Of note is the fact that these vehicles 
are likely traveling at slow speeds, which indicates that even slow-
moving vehicles pose a hazard to crossing and basking snakes. Wallace 
et al. (2008, pp. 243-244) documented a vehicle-related mortality of a 
northern Mexican gartersnake on Arizona State Route 188 near Tonto 
Creek that occurred in 1995. As shown in the above examples, vehicle-
related mortalities of northern Mexican gartersnakes likely occur 
routinely along roads or trails adjacent to occupied habitat throughout 
the range of the subspecies but are generally difficult to document.
    Off-highway vehicle (OHV) use has grown considerably in Arizona. 
For example, as of 2007, 385,000 OHVs were registered in Arizona (a 350 
percent increase since 1998) and 1.7 million people (29 percent of the 
Arizona's public) engaged in off-road activity from 2005-2007 (Sacco 
2007). Over half of OHV users reported that merely driving off-road was 
their primary activity, versus using the OHV for the purpose of 
hunting, fishing, or hiking (Sacco 2007). Given the pervasive use of 
OHV's on the landscape, OHV-related mortalities are likely a threat to 
northern Mexican gartersnakes. Ouren et al. (2007, pp. 16-22) provide 
additional data on the effects of OHV use on wildlife. Specifically, 
OHV use may cause mortality or injury to species, such as northern 
Mexican gartersnakes, that attempt to cross trails created through 
occupied habitat and may even lead to depressed populations of snakes 
depending on the rate of use and number of trails within a given area 
(Ouren et al. 2007, pp. 20-21). This threat may be even more extensive 
from OHVs than from conventional vehicles because OHV trails often 
travel through undeveloped habitat and often cross directly through 
waterbodies. OHV use may also affect northern Mexican gartersnake 
habitat by reducing vegetation cover and plant species diversity, 
reducing infiltration rates, increasing erosion, and reducing habitat 
connectivity (Ouren et al. 2007, pp. 6-7, 11, 16).
    Roads create access to areas that were previously visited only 
infrequently or were inaccessible to humans, increasing the frequency 
and significance of anthropogenic threats to riparian areas and 
fragmenting the landscape, which in addition to direct effects to 
snakes and habitat, may genetically isolate herpetofaunal populations 
(Rosen and Lowe 1994, pp. 146-148; Andrews and Gibbons 2005, p. 772).
    McCranie and Wilson (1987, p. 2) discuss threats to the pine-oak 
communities of higher elevation habitats within the distribution of the 
northern Mexican gartersnake in the Sierra Madre Occidental in Mexico, 
specifically noting that ``* * * the relative pristine character of the 
pine-oak woodlands is threatened * * * every time a new road is 
bulldozed up the slopes in search of new madera or pasturage. Once the 
road is built, further development follows; pueblos begin to pop up 
along its length * * *.'' Several drainages that possess suitable 
habitat for the species occur in the area referenced above by McCranie 
and Wilson (1987, p. 2) including the Rio de la Cuidad, Rio Quebrada El 
Salto, Rio Chico, Rio Las Bayas, Rio El Cigarrero, Rio Galindo, Rio 
Santa Barbara, and the Rio Chavaria.
    While snakes of all species may suffer direct mortality as a result 
of attempting to cross roads, Andrews and Gibbons (2005, pp. 777-779) 
found that many individuals of small, diurnal snake species avoid open 
areas (e.g., roads) instinctively in order to lower predation rates, 
which represents a different type of threat from roads. Shine et al. 
(2004, p. 9) found that the common gartersnake typically changed 
direction when encountering a road. These avoidance behaviors by 
individuals aversive to crossing roads affect movement patterns and may 
ultimately affect reproductive output within populations (Shine et al. 
2004, pp. 9, 17-19). Not crossing roads can reduce the amount of 
habitat available for individual snakes to find

[[Page 71800]]

prey, mates, etc. This avoidance behavior has been observed in the 
common gartersnake (Thamnophis sirtalis), a sister taxon to the Mexican 
gartersnake with similar life histories and behavior (Shine et al. 
2004, p. 9). In our discussion and as evidenced by the literature we 
reviewed on the effect of roads on snake movements, we acknowledge the 
individuality of snakes in their behaviors towards road crossings.
    In addition to altering the movement patterns of some snakes, roads 
interfere with the male gartersnake's olfactory-driven ability to 
follow the pheromone trails left by receptive females (Shine et al. 
2004, pp. 17-18). This effect to the male's ability to efficiently 
trail females may exacerbate the effects of low population density and 
fragmentation that affect several species of snakes, including the 
northern Mexican gartersnake. Because the male gartersnake's ability to 
trail females is hampered by roads, the extra time and distance 
traveled by male snakes seeking receptive females increases exposure to 
predation and subsequently increases mortality rates (Shine et al. 
2004, pp. 18-19). Although the northern Mexican gartersnake was not the 
subject of the 2004 Shine et al. study, similar responses can be 
expected in the northern Mexican gartersnake because its life history 
is similar to the study's subject species (i.e., the common 
gartersnake).
    Roads also affect prey availability for northern Mexican garter 
snakes. Roads tend to adversely affect aquatic breeding anuran 
populations more so than other species due to their activity patterns 
(mass movements of individuals), population structures (large cohorts 
of similarly aged individuals within a population), and preferred 
habitats which are often adjacent to roads and usually constrained to 
aquatic or semiaquatic areas (Hels and Buchwald 2001, p. 331). Carr and 
Fahrig (2001, pp. 1074-1076) found that populations of highly mobile 
anuran species such as leopard frogs (Rana pipiens) were run over more 
frequently than more sedentary species and that population persistence 
can be at risk depending on traffic densities, which may adversely 
affect the prey base for northern Mexican gartersnakes because leopard 
frogs are a primary prey species.
    Recreation. As discussed above, population growth trends are 
expected to continue into the future. Expanding population growth leads 
to higher recreational use of riparian areas, as evidenced along 
reaches of the Salt and Verde rivers in proximity to the Phoenix 
metropolitan area. Riparian areas located near urban areas are 
vulnerable to the effects of increased recreation with predictable 
changes in the type and intensity of land use following residential 
development. An example of such an area within the existing 
distribution of the northern Mexican gartersnake is the Verde Valley. 
The reach of the Verde River that winds through the Verde Valley 
receives a high amount of recreational use from people living in 
central Arizona (Paradzick et al. 2006, pp. 107-108). Increased human 
use results in the trampling of near-shore vegetation, which reduces 
cover for gartersnakes, especially newborns. Increased human visitation 
in occupied habitat also increases the potential for human-gartersnake 
interactions, which frequently leads to the capture, injury, or death 
of the snake (Rosen and Schwalbe 1988, p. 43; Ernst and Zug 1996, p. 
75; Green 1997, pp. 285-286; Nowak and Santana-Bendix 2002, p. 39). 
Recreational activities in the Southwest are often tied to water bodies 
and riparian areas. Increased recreational impacts on the quantity and 
quality of water, as well as the adjacent vegetation, are threats to 
local populations of the northern Mexican gartersnake.
    Groundwater Pumping, Surface Water Diversions, and Flood Control. 
Increased urbanization and population growth results in an increase in 
the demand for water and, therefore, water development projects. 
Collier et al. (1996, p. 16) mention that water development projects 
are one of two main causes of decline of native fish in the Salt and 
Gila rivers of Arizona. Municipal water use in central Arizona has 
increased by 39 percent in the last 8 years (American Rivers 2006). 
Water for development and urbanization is often supplied by groundwater 
pumping and surface water diversions from sources that include 
reservoirs and Central Arizona Project's allocations from the Colorado 
River. The hydrologic connection between groundwater and surface flow 
of intermittent and perennial streams is becoming better understood. 
Groundwater pumping creates a cone of depression within the affected 
aquifer that slowly radiates outward from the well site. When the cone 
of depression intersects the hyporheic zone of a stream (the active 
transition zone between two adjacent ecological communities under or 
beside a stream channel or floodplain between the surface water and 
groundwater that contributes water to the stream itself), the surface 
water flow may decrease, and the subsequent drying of riparian and 
wetland vegetative communities can follow. This situation has been 
created by groundwater use by the community of Sierra Vista in Cochise 
County, which continues to threaten the riparian community along the 
upper San Pedro River where the northern Mexican gartersnake 
historically occurred. Continued groundwater pumping at such levels 
draws down the aquifer sufficiently to create a water-level gradient 
away from the stream and floodplain (Webb and Leake 2005, p. 309). 
Finally, complete disconnection of the aquifer and the stream results 
in strong negative effects to riparian vegetation (Webb and Leake 2005, 
p. 309). If complete disconnection occurs, the hyporheic zone could be 
adversely affected. The hyporheic zone can promote ``hot spots'' of 
productivity where groundwater upwelling produces nitrates that can 
enhance the growth of vegetation, but its significance is contingent 
upon its activity and extent of connection with the groundwater 
(Boulton et al. 1998, p. 67; Boulton and Hancock 2006, pp. 135, 138). 
Such ``hot spots'' can enhance the quality of northern Mexican 
gartersnake habitat. Conversely, changes to the duration and timing of 
upwelling can potentially lead to localized extinctions in biota 
(Boulton and Hancock 2006, p. 139), reducing gartersnake habitat 
suitability.
    The effects of groundwater pumping on surface water flow and 
riparian communities have been observed in the Santa Cruz, San Pedro, 
and Verde rivers as a result of groundwater demands of Tucson, Sierra 
Vista, and the rapidly growing Prescott Valley, respectively (Stromberg 
et al. 1996, pp. 113, 124-128; Rinne et al. 1998, p. 9; Voeltz 2002, 
pp. 45-47, 69-71). Along the upper San Pedro River, Stromberg et al. 
(1996, pp. 124-127) found that wetland herbaceous species, important as 
cover for northern Mexican gartersnakes, are the most sensitive to the 
effects of a declining groundwater level. Webb and Leake (2005, pp. 
302, 318-320) described a correlative trend regarding vegetation along 
southwestern streams from historically being dominated by marshy 
grasslands preferable to northern Mexican gartersnakes, to currently 
being dominated by woody species more tolerant of declining water 
tables due to their associated deeper rooting depths.
    The full effects of large-scale groundwater pumping associated with 
the proposed Big Chino Water Ranch Project and its associated 30-mile 
(48-km), 36-in (91-cm) diameter pipeline have yet to be realized in the 
Verde River (McKinnon 2006c). This groundwater pumping and inter-basin 
transfer project is projected to deliver

[[Page 71801]]

2.8 billion gallons of groundwater annually from the Big Chino sub-
basin aquifer to the rapidly growing area of Prescott Valley for 
municipal use (McKinnon 2006c). The Big Chino sub-basin provides 86 
percent of the baseflow to the upper Verde River (American Rivers 2006; 
McKinnon 2006a). The potential for this project to obtain funding and 
approval for implementation has placed the Verde River on American 
River's 2006 ``Ten Most Endangered Rivers List'' (American Rivers 
2006). This potential reduction or loss of baseflow in the Verde River 
could seasonally dry up large reaches or adversely affect the riparian 
community and the suitability of the habitat for remaining populations 
of the northern Mexican gartersnake and its prey species in that area.
    Within the Verde River watershed, and particularly within the Verde 
Valley where the northern Mexican gartersnake is believed to currently 
remain, several other activities continue to threaten surface flows 
(Rinne et al. 1998, p. 9; Paradzick et al. 2006, pp. 104-110). The 
demands for surface water allocations from rapidly growing communities 
and agricultural and mining interests have altered flows or dewatered 
significant reaches during the spring and summer months in some of the 
Verde River's larger, formerly perennial tributaries such as Wet Beaver 
Creek, West Clear Creek, and the East Verde River, which may have 
supported the northern Mexican gartersnake (Girmendock and Young 1993, 
pp. 45-47; Sullivan and Richardson 1993, pp. 38-39; Paradzick et al. 
2006, pp. 104-110). Groundwater pumping in the Tonto Creek drainage 
regularly eliminates surface flows during parts of the year (Abarca and 
Weedman 1993, p. 2). The upper Gila River is also threatened by water 
diversions and water allocations. In New Mexico, a proposed water 
project that resulted from a landmark Gila River water settlement in 
2004 allows New Mexico the right to withhold 4.5 billion gallons of 
surface water every year (McKinnon 2006d). If this proposed water 
diversion project is implemented, in dry years, currently perennial 
reaches of the upper Gila River will dry completely, which removes all 
suitability of this habitat for the northern Mexican gartersnakes and a 
host of other riparian and aquatic species (McKinnon 2006d).
    The Arizona Department of Water Resources (ADWR) manages water 
supplies in Arizona and has established five Active Management Areas 
(AMA) across the State (ADWR 2006). An AMA is established by ADWR when 
an area's water demand has exceeded the groundwater supply and an 
overdraft has occurred. In these areas, groundwater use has exceeded 
the rate that precipitation can recharge the aquifer, which leads to 
conditions described above. Geographically, all five AMAs overlap the 
historical distribution of the northern Mexican gartersnake in Arizona. 
The declaration of these AMAs further illustrates the condition and 
future threats to riparian habitat in these areas and are a cause of 
concern for the long-term maintenance of historical and occupied 
northern Mexican gartersnake habitat. Such overdrafts reduce surface 
water flow of streams that are hydrologically connected to the aquifer 
under stress, which can be further exacerbated by the surface water 
diversions.
    To accommodate the needs of rapidly growing rural and urban 
populations, surface water is commonly diverted to serve many 
industrial and municipal uses. These water diversions have dewatered 
large reaches of once perennial or intermittent streams, adversely 
affecting northern Mexican gartersnake habitat throughout its range in 
Arizona and New Mexico. Many tributaries of the Verde River are 
permanently or seasonally dewatered by water diversions for agriculture 
(Paradzick et al. 2006, pp. 104-110).
    Effects from flood control projects threaten riparian and aquatic 
habitat, as well as threaten the northern Mexican gartersnake directly. 
Kimmell (2008), Gila County Board of Supervisors (2008), Trammell 
(2008), and Sanchez (2008) all discuss a growing concern of residents 
that live within or adjacent to the floodplain of Tonto Creek in Gila 
County, Arizona, both upstream and downstream of the town of Gisela, 
Arizona. Specifically, there is growing concern to address threats to 
private property and associated infrastructure posed by flooding of 
Tonto Creek (Sanchez 2008). The only known remaining population of 
northern Mexican gartersnakes within the large Salt River watershed 
occurs on Tonto Creek. The status of the northern Mexican gartersnake 
on tribal lands within the Salt River watershed remains unknown. In 
Resolution No. 08-06-02, the Gila County Board of Supervisors has 
proactively declared a state of emergency within Gila County as a 
result of the expectation for heavy rain and snowfall causing 
repetitive flooding conditions (Gila County Board of Supervisors 2008). 
In response, the Arizona Division of Emergency Management called 
meetings and initiated discussions among stakeholders in an attempt to 
mitigate these flooding concerns (Kimmell 2008, Trammell 2008). 
Mitigation measures that have been discussed include removal of 
riparian vegetation, removal of debris piles, potential channelization 
of Tonto Creek, improvements to existing flood control structures or 
addition of new structures, and the construction of new bridges. 
Adverse effects of these types of activities to aquatic and riparian 
habitat and to the northern Mexican gartersnake or its prey species 
will result from the physical alteration or destruction of habitat, 
significant increases to flow velocity, and removal of key foraging 
habitat and areas to hibernate, such as debris jams. Specifically, 
flood control projects permanently alter stream flow characteristics 
and have the potential to make the stream unsuitable as habitat for the 
northern Mexican gartersnake by reducing or eliminating stream 
sinuosity and associated pool and backwater habitats that are critical 
to northern Mexican gartersnakes and their prey species. Threats 
presented by these flood control planning efforts are considered 
imminent.
    In Mexico, Conant (2003, p. 4) noted human-caused threats to seven 
fragmented, highly localized subspecies of Mexican gartersnake in the 
Transvolcanic Belt Region of southern Mexico, which extends from 
southern Jalisco eastward through the State of Mexico to central 
Veracruz. Although this is a relatively small area, rural land uses are 
widespread in the region and these threats can be extrapolated to other 
areas of that region within the distribution of the northern Mexican 
gartersnake in Mexico. Some of these threats included water diversions, 
pollution (e.g., discharge of raw sewage), sedimentation of aquatic 
habitats, and increased dissolved nutrients, resulting in decreased 
dissolved oxygen, in still-water habitats. Conant (2003, p. 4) stated 
that many of these threats were evident during his field work in the 
1960s, but that they are ``continuing with increased velocity.''
    Water pollution, dams, groundwater pumping, and impoundments were 
identified by Miller et al. (2005, pp. 60-61) as significant threats to 
aquatic biota in Mexico. Miller et al. (2005, p. 60) stated that 
``During the time we have collectively studied fishes in M[eacute]xico 
and southwestern United States, the entire biotas of long reaches of 
major streams where the northern Mexican gartersnake is distributed, 
such as the R[iacute]o Grande de Santiago below Guadalajara (Jalisco) 
and R[iacute]o Colorado (lower Colorado River in Mexico) downstream of 
Hoover (Boulder) Dam (in the United States), have simply been destroyed 
by pollution and river

[[Page 71802]]

alteration.'' Near Torre[oacute]n, Coahuila, where the northern Mexican 
gartersnake occurs, groundwater pumping has resulted in flow reversal, 
which has dried up many local springs, drawn arsenic-laden water to the 
surface, and resulted in adverse human health effects in that area. 
Severe water pollution from untreated domestic waste is evident 
downstream of large Mexican cities, such as Mexico City, and inorganic 
pollution from nearby industrialized areas and agricultural irrigation 
return flow has dramatically affected aquatic communities through 
contamination (Miller et al. 2005, p. 60). Miller et al. (2005, p. 61) 
provides an excerpt from Soto Galera et al. (1999) addressing the 
threats to the R[iacute]o Lerma, Mexico's longest river, and which is 
occupied by the northern Mexican gartersnake: ``The basin has 
experienced a staggering amount of degradation during the 20th Century. 
By 1985-1993, over half of our study sites had disappeared or become so 
polluted that they could no longer support fishes. Only 15 percent of 
the sites were still capable of supporting sensitive species. Forty 
percent (17 different species) of the native fishes of the basin had 
suffered major declines in distribution, and three species may be 
extinct. The extent and magnitude of degradation in the R[iacute]o 
Lerma basin matches or exceeds the worst cases reported for comparably 
sized basins elsewhere in the world.''
    Several rivers within the historical range of the northern Mexican 
gartersnake have been impounded and dammed throughout Mexico, resulting 
in habitat modification and the dispersal and establishment of 
nonnative species. The damming and modification of the lower Colorado 
River in Mexico, where the northern Mexican gartersnake occurred, has 
facilitated the replacement of the entire native fishery with nonnative 
species (Miller et al. 2005, p. 61). Nonnative species continue to pose 
significant threats in the decline of native, often highly localized, 
prey species of the northern Mexican gartersnake, as discussed further 
in Factor C below (Miller et al. 2005, p. 60).
    Miller et al. (2005) provide information on threats to freshwater 
fishes, and riparian and aquatic communities in specific waterbodies 
throughout Mexico that are within the historical range of the northern 
Mexican gartersnake: The R[iacute]o Grande (dam construction, p. 78 and 
extirpations of freshwater fish species, pp. 82, 112); headwaters of 
the R[iacute]o Lerma (extirpation of freshwater fish species, nonnative 
species, pollution, dewatering, pp. 60, 105, 197); Lago de Chapala and 
its outlet to the R[iacute]o Grande de Santiago (major declines in 
freshwater fish species, p. 106); medium-sized streams throughout the 
Sierra Madre Occidental (localized extirpations, logging, dewatering, 
pp. 109, 177, 247); the Rio Conchos (extirpations of freshwater fish 
species, p. 112); the r[iacute]os Casas Grandes, Santa Mar[iacute]a, 
del Carmen, and Laguna Bustillos (water diversions, groundwater 
pumping, channelization, flood control practices, pollution, and 
introduction of nonnative species, pp. 124, 197); the R[iacute]o Santa 
Cruz (extirpations, p. 140); the R[iacute]o Yaqui (nonnative species, 
pp. 148, Plate 61); the R[iacute]o Colorado (nonnative species, p. 
153); the r[iacute]os Fuerte and Culiac[aacute]n (logging, p. 177); 
canals, ponds, lakes in the Valle de M[eacute]xico (nonnative species, 
extirpations, pollution, pp. 197, 281); the R[iacute]o Verde Basin 
(dewatering, nonnative species, extirpations, Plate 88); the R[iacute]o 
Mayo (dewatering, nonnative species, p. 247); the R[iacute]o Papaloapan 
(pollution, p. 252); lagos de Zacapu and Yuriria (habitat destruction, 
p. 282); and the R[iacute]o P[aacute]nuco Basin (nonnative species, p. 
295).
    Conant (1974, pp. 486-489) described significant threats to 
northern Mexican gartersnake habitat within its distribution in western 
Chihuahua, Mexico, and within the Rio Concho system where it occurs. 
These threats included impoundments, water diversions, and purposeful 
introductions of largemouth bass, common carp, and bullfrogs. We 
discuss the threats from nonnative species introductions below in our 
discussion of Factor C.
    Clearly, water quality and quantity are being affected by ongoing 
activities in the United States and Mexico. Due to the reliance of the 
northern Mexican gartersnake on ecosystems and communities supported by 
permanent water sources, these threats are significant to the survival 
and viability of existing and future northern Mexican gartersnake 
populations.
    Improper Livestock Grazing and Agricultural Uses. In a number of 
ways described below, poorly managed livestock grazing has damaged 
approximately 80 percent of stream, cienega, and riparian ecosystems in 
the western United States (Kauffman and Krueger 1984, pp. 433-435; 
Weltz and Wood 1986, pp. 367-368; Waters 1995, pp. 22-24; Pearce et al. 
1998, p. 307; Belsky et al. 1999, p. 1). Fleischner (1994, p. 629) 
found that ``Because livestock congregate in riparian ecosystems, which 
are among the most biologically rich habitats in arid and semiarid 
regions, the ecological costs of grazing are magnified at these 
sites.'' Stromberg and Chew (2002, p. 198) and Trimble and Mendel 
(1995, p. 243) also discussed the propensity for poorly managed cattle 
to remain within or adjacent to riparian communities. Trimble and 
Mendel (1995, p. 243) stated that ``Cows, unlike sheep, appear to love 
water and spend an inordinate amount of time together lounging in 
streams and ponds, especially in summer (surface-active season for 
reptiles and amphibians), sometimes going in and coming out several 
times in the course of a day.'' Expectedly, this behavior is more 
pronounced in more arid regions (Trimble and Mendel 1995, p. 243). In 
one rangeland study, it was concluded that 81 percent of the vegetation 
that was consumed, trampled, or otherwise removed was from a riparian 
area, which amounted to only 2 percent of the total grazing space 
(Trimble and Mendel 1995, p. 243). Another study reported that grazing 
rates were 5 to 30 times higher in riparian areas than on the uplands, 
which may be due in part to several factors: (1) Higher forage volume 
and palatability of species in riparian areas; (2) water availability; 
(3) the close proximity of riparian areas to the best upland grazing 
sites; and (4) microclimatic features such as cooler temperatures and 
shade (Trimble and Mendel 1995, p. 244).
    Effects of improper livestock management on riparian and aquatic 
communities have spanned from early settlement to modern day. Some 
historical accounts of riparian area conditions in Arizona clarify 
early effects of poor livestock management. Cheney et al. (1990, pp. 5, 
10) provide historical accounts of the early adverse effects of 
improper livestock management in the riparian zones and adjacent 
uplands of the Tonto National Forest and in south-central Arizona. 
These accounts describe the removal of riparian trees for preparation 
of livestock use and substantial changes to flow regimes accentuated by 
observed increases in runoff and erosion rates. Such accounts of 
riparian conditions within the historical distribution of the northern 
Mexican gartersnake in Arizona contribute to the understanding of when 
declines in abundance and distribution may have occurred and the 
contributions of this factor to the subsequent fragmentation of 
populations and widespread extirpations.
    Poor livestock management causes a decline in diversity, abundance, 
and species composition of riparian herpetofauna communities from 
direct or indirect threats to the prey base, the habitat, or to the 
northern Mexican

[[Page 71803]]

gartersnake. These effects include: (1) Declines in the structural 
richness of the vegetative community; (2) losses or reductions of the 
prey base; (3) increased aridity of habitat; (4) loss of thermal cover 
and protection from predators; and (5) a rise in water temperatures to 
levels lethal to larval stages of amphibian and fish development (Szaro 
et al. 1985, p. 362; Schulz and Leininger 1990, p. 295; Belsky et al. 
1999, pp. 8-11). Improper livestock grazing may also lead to 
desertification (the process of becoming arid land or desert as a 
result of land mismanagement or climate change) due to a loss in soil 
fertility from erosion and gaseous emissions spurred by a reduction in 
vegetative ground cover (Schlesinger et al. 1990, p. 1043).
    Szaro et al. (1985, p. 360) assessed the effects of improper 
livestock management on a sister taxon. They found that western 
(terrestrial) gartersnake (Thamnophis elegans vagrans) populations were 
significantly higher (versus controls) in terms of abundance and 
biomass in areas that were excluded from grazing, where the streamside 
vegetation remained lush, than where uncontrolled access to grazing was 
permitted. This effect was complemented by higher amounts of cover from 
organic debris from ungrazed shrubs that accumulate as the debris moves 
downstream during flood events. Specifically, results indicated that 
snake abundance and biomass were significantly higher in ungrazed 
habitat, with a five-fold difference in number of snakes captured, 
despite the difficulty of making observations in areas of increased 
habitat complexity (Szaro et al. 1985, p. 360). Szaro et al. (1985, p. 
362) also noted the importance of riparian vegetation for the 
maintenance of an adequate prey base and as cover in thermoregulation 
and predation avoidance behaviors, as well as for foraging success.
    Watersheds where improper grazing has been documented as a 
contributing factor of northern Mexican gartersnake declines include 
the Verde, Salt, Agua Fria, San Pedro, Gila, and Santa Cruz 
(Hendrickson and Minckley 1984, pp. 140, 152, 160-162; Rosen and 
Schwalbe 1988, pp. 32-33; Girmendock and Young 1997, p. 47; Voeltz 
2002, pp. 45-81; Krueper et al. 2003, pp. 607, 613-614; Holycross et 
al. 2006, pp. 52-61; McKinnon 2006d, 2006e; Paradzick et al. 2006, pp. 
90-92; USFS 2008). Holycross et al. (2006, pp. 53-55, 58) recently 
documented adverse effects from improper livestock grazing on northern 
Mexican gartersnake habitat along the Agua Fria from EZ Ranch to Bloody 
Basin Road, along Dry Creek from Dugas Road to Little Ash Creek, along 
Little Ash Creek from Brown Spring to Dry Creek, along Sycamore Creek 
in the vicinity of its confluence with the Verde River, and on 
potential northern Mexican gartersnake habitat along Pinto Creek at the 
confluence with the West Fork of Pinto Creek. In southeastern Arizona, 
there have been observations of effects to the vegetative community 
suggesting that livestock grazing activities continue to adversely 
affect remaining populations of northern Mexican gartersnakes by 
reducing or eliminating cover required by the northern Mexican 
gartersnake for thermoregulation, protection from predation, and 
foraging (Hale 2001, pp. 32-34, 50, 56).
    To increase forage and stocking rates for livestock production in 
the arid lowlands of northern Mexico, African buffelgrass was widely 
introduced in Mexico and has subsequently spread via its own natural 
means of dispersal (B[uacute]rquez-Montijo et al. 2002, p. 131; Nijhuis 
2007, pp. 1-7). Buffelgrass invasions pose a serious threat to native 
arid ecosystems because buffelgrass prevents germination of native 
plant species, competes for water, crowds out native vegetation, and 
creates fine fuels in vegetation communities not adapted to fire. In 
such native arid ecosystems, buffelgrass has caused many changes, 
including severe soil erosion resulting from an increase in the number 
and severity of fires (B[uacute]rquez-Montijo et al. 2002, pp. 135, 
138). Erosion affects the suitability of habitat for northern Mexican 
gartersnakes and their prey species by increasing the turbidity of 
streams and filling in important pool habitat, which increases the 
water temperature of pools, lowers the dissolved oxygen content of the 
water, and reduces their permanency. Recent estimates indicate that 80 
percent of Mexico is affected by soil erosion caused by vegetation 
removal related to grazing, fires, agriculture, deforestation, etc. The 
most serious erosion is occurring in the States of Guanajuato (43 
percent of the State's land area), Jalisco (25 percent of the State's 
land area), and M[eacute]xico (25 percent of the State's land area) (va 
Landa et al. 1997, p. 317), the states in which the northern Mexican 
gartersnake occurs.
    The effects of stock tanks associated with livestock grazing on 
northern Mexican gartersnakes depend on how they are managed. Dense 
bank and aquatic vegetation is an important habitat characteristic for 
the northern Mexican gartersnake that can be affected if the 
impoundment is poorly managed, which may lead to trampling or 
overgrazing of the bankside vegetation. Alternatively, well-managed 
stock tanks can provide habitat suitable for northern Mexican 
gartersnakes both structurally and in terms of prey base, especially 
when the tank remains devoid of nonnative species while supporting 
native prey species; provides adequate vegetation cover; and provides 
reliable water sources in periods of prolonged drought. Given these 
benefits of well-managed stock tanks, we believe well-managed stock 
tanks may be an important component to northern Mexican gartersnake 
conservation.
    Direct mortality of amphibian species, in all life stages, from 
being trampled by livestock has been documented in the literature 
(Bartelt 1998, p. 96; Ross et al. 1999, p. 163). The resultant 
extirpation risk of amphibian populations as a prey base for northern 
Mexican gartersnakes by direct mortality is governed by the relative 
isolation of the amphibian population, the viability of that 
population, and the propensity for stochastic events such as wildfires. 
Livestock grazing within habitat occupied by northern Mexican 
gartersnakes can result in direct mortality of individual gartersnakes 
as observed in a closely related taxon on the Apache-Sitgreaves 
National Forest. In that instance, a black-necked gartersnake 
(Thamnophis cyrtopsis cyrtopsis) had apparently been killed by 
trampling by cattle along the shore of a stock tank within an actively 
grazed allotment (Chapman 2005). This event was not observed first-
hand, but was supported by postmortem photographic documentation of the 
physical injuries to the specimen and the location of the carcass among 
a dense cluster of hoof tracks along the shoreline of the stock tank. 
It is also unlikely that a predator would kill the snake and leave it 
uneaten. While this type of direct mortality of gartersnakes has long 
been suspected by agency biologists and academia, this may be the first 
recorded observation of direct mortality of a gartersnake due to 
livestock trampling. We expect this type of direct mortality to be 
uncommon but significant in the instance of a fragmented population 
with a skewed age-class distribution (large adults), without a 
neighboring source population to assist with recolonization, and low to 
no recruitment as currently observed in many northern Mexican 
gartersnake populations in the United States. In these circumstances, 
the loss of one or more adults, most notably reproductive females, may 
lead directly to extirpation of the species from a given site with no 
expectation of recolonization.
    Poor forestry and agricultural practices were cited as the largest 
and

[[Page 71804]]

most widespread threats to the native fisheries of the Jalisco and 
Colima area in Mexico investigated by Lyons and Navarro-Perez (1990, p. 
37), affecting prey availability for northern Mexican gartersnakes in 
areas where they occur. Lyons and Navarro-Perez (1990, p. 37) indicated 
that in high-elevation areas, clear-cutting of trees and unrestricted 
livestock grazing have increased erosion and sedimentation. They 
suspected impacts on fish and invertebrate populations had occurred. In 
lowland areas, Lyons and Navarro-Perez (1990, p. 37) cited diversion of 
water for irrigation, runoff from cultivated fields, and runoff from 
small towns and villages as causing additional environmental 
degradation. Lyons and Navarro-Perez (1990, p. 37) found that the 
tolerance of several fish species to degradation depended on the form 
of degradation.
    Minckley et al. (2002, pp. 687-705) described three new species of 
pupfish and provided a summary of threats (p. 696) to these species and 
their habitat in Chihuahua, Mexico, within the distribution of the 
northern Mexican gartersnake. Initial settlement and agricultural 
development of the area resulted in significant channel cutting through 
soil layers protecting the alluvial plain above them, which resulted in 
reductions in the base level of each basin in succession (Minckley et 
al. 2002, p. 696). Related to these activities, the building of dams 
and diversion structures dried entire reaches of some regional streams 
and altered flow patterns of others (Minckley et al. 2002, p. 696). 
This was followed by groundwater pumping (enhanced by the invention of 
the electric pump) which lowered groundwater levels and dried-up 
springs and small channels and reduced the reliability of baseflow in 
``essentially all systems'' (Minckley et al. 2002, p. 696). 
Subsequently, the introduction and expansion of nonnative species in 
the area successfully displaced or extirpated many native species 
(Minckley et al. 2002, p. 696).
    Our analysis of the best available scientific and commercial 
information available indicates that adverse effects from improper 
livestock management on the northern Mexican gartersnake, its habitat, 
and its prey base can be significant, especially when combined with 
other threats, most notably nonnative species (discussed below under 
Factor C). Preliminary gartersnake survey data from Burger (2008) from 
the States of Durango and southern Chihuahua, Mexico, indicate that the 
northern Mexican gartersnake is less susceptible to population impacts 
associated with physical disturbances to its habitat, such as livestock 
grazing, when the biotic community is comprised of wholly native 
species. However, even modest alterations in the physical habitat of 
the northern Mexican gartersnake may lead to population declines, or 
even extirpations, when these adverse effects act in combination with 
the adverse effects of nonnative species. In Mexico, livestock grazing, 
often in association with deforestation and crop cultivation, are also 
having adverse affects on the northern Mexican gartersnake. We 
recognize that well-managed grazing can occur with limited effects to 
this species when the presence or absence of nonnative species is 
considered, and management emphasis is directed towards limiting some 
access to riparian and aquatic habitats within occupied habitat. These 
actions, combined with management that disperses livestock away from 
riparian areas, reduce the threats of livestock grazing on northern 
Mexican gartersnakes and their habitats. As previously stated, we also 
recognize well-managed stock tanks as a valuable tool in the 
conservation of northern Mexican gartersnakes.
    Additional information on the effects of improper livestock grazing 
to the northern Mexican gartersnake and its habitat can be found in our 
2006, 12-month finding for this species (71 FR 56227) and in Sartz and 
Tolsted (1974, p. 354); Szaro et al. (1985, pp. 360, 362, 364); Weltz 
and Wood (1986, pp. 367-368); Rosen and Schwalbe (1988, pp. 32-33, 47); 
Clary and Webster (1989, p. 1); Clary and Medin (1990, p. 1); Schulz 
and Leininger (1990, p. 295); Schlesinger et al. (1990, p. 1043); 
Orodho et al. (1990, p. 9); Fleischner (1994, pp. 629, 631-632); 
Trimble and Mendel (1995, pp. 235-236, 243-244); Pearce et al. (1998, 
p. 302); Belsky et al. (1999, pp. 8-11); Stromberg and Chew (2002, p. 
198); and Krueper et al. (2003, pp. 607, 613-614).
    High-Intensity Wildfires. Low-intensity fire has been a natural 
disturbance factor in forested landscapes for centuries, and low-
intensity fires were common in southwestern forests prior to European 
settlement (Rinne and Neary 1996, pp. 135-136). Rinne and Neary (1996, 
p. 143) discuss the current effects of fire management policies on 
aquatic communities in Madrean Oak Woodland biotic communities in the 
southwestern United States. They concluded that existing wildfire 
suppression policies intended to protect the expanding number of human 
structures on forested public lands have altered the fuel loads in 
these ecosystems and increased the probability of devastating 
wildfires. The effects of these catastrophic wildfires include the 
removal of vegetation, the degradation of watershed condition, altered 
stream behavior, and increased sedimentation of streams. These effects 
can harm fish communities, as observed in the 1990 Dude Fire, when 
corresponding ash flows decimated some fish populations in Dude Creek 
and the East Verde River (Voeltz 2002, p. 77), which, ultimately, 
affects habitat suitability for the gartersnake. These effects can 
significantly reduce the prey base for northern Mexican gartersnakes 
and could lead to direct mortality in the case of high-intensity fires 
that are within occupied habitat. The Chiricahua leopard frog recovery 
plan cites altered fire regimes as a serious threat to Chiricahua 
leopard frogs, a prey species for northern Mexican gartersnakes (USFWS 
2008, pp. 38-39).
    Fire has also become an increasingly significant threat in lower 
elevation communities as well. Esque and Schwalbe (2002, pp. 180-190) 
discuss the effect of wildfires in the upper and lower subdivisions of 
Sonoran desertscrub where the northern Mexican gartersnake historically 
occurred. The widespread invasion of nonnative annual grasses, such as 
brome species (Bromus sp.) and Mediterranean grasses (Schismus sp.), 
appear to be largely responsible for altered fire regimes that have 
been observed in these communities, which are not adapted to fire 
(Esque and Schwalbe 2002, p. 165). African buffelgrass (Pennisetum 
ciliare) is recognized as another invading nonnative plant species 
throughout the lower elevations of northern Mexico and Arizona. Nijhuis 
(2007, pp. 1-7) discuss the spread of nonnative buffelgrass within the 
Sonoran Desert of Arizona and adjoining Mexico, citing the grass' 
ability to out compete native vegetation and present significant risks 
of fire in an ecosystem that is not adapted to fire. In areas comprised 
entirely of native species, ground vegetation density is mediated by 
barren spaces that do not allow fire to carry itself across the 
landscape. However, in areas where nonnative grasses have become 
established, the fine fuel load is continuous, and fire is capable of 
spreading quickly and efficiently (Esque and Schwalbe 2002, p. 175).
    After disturbances such as fire, nonnative grasses may exhibit 
dramatic population explosions, which hasten their effect on native 
vegetative communities. Additionally, with increased fire frequency, 
these population explosions ultimately lead to a type-conversion of the 
vegetative

[[Page 71805]]

community from desertscrub to grassland (Esque and Schwalbe 2002, pp. 
175-176). Fires carried by the fine fuel loads created by nonnative 
grasses often burn at unnaturally high temperatures, which may result 
in soils becoming hydrophobic (water repelling), exacerbate sheet 
erosion, and contribute large amounts of sediment to receiving water 
bodies, thereby affecting the health of the riparian community (Esque 
and Schwalbe 2002, pp. 177-178). The siltation of isolated, remnant 
pools in intermittent streams significantly affects lower elevation 
species by increasing the water temperature, reducing dissolved oxygen, 
and reducing or eliminating the permanency of pools, as observed in 
pools occupied by lowland leopard frogs and native fish, important prey 
species for northern Mexican gartersnakes (Esque and Schwalbe 2002, p. 
190).
    Undocumented Immigration and International Border Enforcement and 
Management. Undocumented immigrants and smugglers attempt to cross the 
International border from Mexico into the United States in areas 
historically and currently occupied by the northern Mexican 
gartersnake. These illegal border crossings and the corresponding 
efforts to enforce U.S. border laws and policies have been occurring 
for many decades with increasing intensity and have resulted in 
unintended adverse effects to biotic communities in the border region. 
During the warmest months of the year, many attempted border crossings 
occur in riparian areas that serve to provide shade, water, and cover. 
Increased U.S. border enforcement efforts that began in the early 1990s 
in California and Texas have resulted in a shift in crossing patterns 
and increasingly concentrated levels of attempted illegal border 
crossings into Arizona (Segee and Neeley 2006, p. 6).
    Riparian habitats that historically supported or may currently 
support northern Mexican gartersnakes in the San Bernardino National 
Wildlife Refuge, the San Pedro River corridor, the Santa Cruz River 
corridor, the lower Colorado River corridor, and along many smaller 
streamside and canyon bottom areas within Cochise, Santa Cruz, and Pima 
counties have high levels of undocumented immigrant traffic (Segee and 
Neeley 2006, Executive Summary, pp. 10-12, 21-23).
    Traffic on new roads and trails from illegal border crossing and 
enforcement activities, as well as the construction, use, and 
maintenance of enforcement infrastructure (i.e., fences, walls, and 
lighting systems), leads to compaction of streamside soils, and the 
destruction and removal of riparian vegetation necessary as cover for 
the northern Mexican gartersnake. Current border infrastructure 
projects, including vehicle barriers and pedestrian fences, are located 
specifically in valley bottoms and have resulted in direct impacts to 
water courses and altered drainage patterns affecting northern Mexican 
gartersnake habitat (USFWS 2008, p. 4). These activities also produce 
sediment in streams, which affects their suitability as habitat for 
prey species of the northern Mexican gartersnake by reducing their 
permanency and altering their physical and chemical parameters. 
Riparian areas along the upper San Pedro River have been impacted by 
abandoned fires that undocumented immigrants started to keep warm or 
prepare food (Segee and Neeley 2006, p. 23). There is also the threat 
of pursuit, capture, and death of northern Mexican gartersnakes when 
they are encountered by illegal border crossers and border enforcement 
personnel in high-use areas due to the snake's stigma in society (Rosen 
and Schwalbe 1988, p. 43; Ernst and Zug 1996, p. 75; Green 1997, pp. 
285-286; Nowak and Santana-Bendix 2002, p. 39).
    The wetland habitat within the San Bernardino National Wildlife 
Refuge provides habitat for the northern Mexican gartersnake, where it 
is now likely extirpated, and has been adversely affected by 
undocumented immigration. It is estimated that approximately 1,000 
undocumented immigrants per month use these important wetlands for 
bathing, drinking, and other uses during their journey northward (Segee 
and Neeley 2006, pp. 21-22). These activities occur in other border 
areas, such as the Santa Cruz River, where the northern Mexican 
gartersnake occurs, although they have not been quantified (Segee and 
Neeley 2006, pp. 21-22). They can contaminate the water quality of the 
wetlands and lead to reductions in the prey base for the northern 
Mexican gartersnake, as well as increase exposure of the snake to 
humans, and thereby increase direct mortality rates (Rosen and Schwalbe 
1988, p. 43; Ernst and Zug 1996, p. 75; Green 1997, pp. 285-286; Nowak 
and Santana-Bendix 2002, p. 39; Segee and Neeley 2006, pp. 21-22). In 
addition, numerous observations of littering and destruction of 
vegetation and wildlife occur annually throughout the San Bernardino 
National Wildlife Refuge, which adversely affect the quality and 
quantity of vegetation as habitat for the northern Mexican gartersnake 
(USFWS 2006, p. 95). Due to the immediate proximity of the upper Santa 
Cruz River to the international border and the effect of border control 
operations that funnel undocumented immigrants into rural environments, 
we conclude that these adverse effects likely occur in this area, which 
is occupied by the northern Mexican gartersnake.
    Threats from illegal border crossers appear to have increased in 
recent years within the Coronado National Forest of southern Arizona 
(USFS 2008). Reports of significant water pollution from bathing 
activities by undocumented immigrants in habitat occupied by northern 
Mexican gartersnakes have been received (USFS 2008). Of particular 
concern to USFS (2008), was the concentrated use of pools by 
undocumented immigrants during the warmest months before summer rains 
commence, when the habitat is also critical to the northern Mexican 
gartersnake and its prey. The amount of surface water is generally 
considered the lowest during the early summer, pre-monsoon months in 
Arizona, which compounds the effects of the use of pools for bathing by 
concentrating water contamination in the limited habitat available to 
northern Mexican gartersnakes and their prey species. Because of the 
limited amount of alternative habitat, illegal border crossers and 
gartersnakes are concentrated in the same areas, increasing encounter 
rates and the potential threats to northern Mexican gartersnakes.
    Summary of Factor A. Riparian and aquatic habitats that are 
essential for the survival of the northern Mexican gartersnake are 
being negatively impacted throughout the subspecies' range. Threats 
including water diversions, groundwater pumping, dams, channelization, 
and erosion-related effects are occurring in both the United States and 
Mexico that affect the amount of water within occupied northern Mexican 
gartersnake habitat, directly affecting its suitability for northern 
Mexican gartersnakes. Threats from development, roads, flood control 
and water diversion, improper livestock grazing, high-intensity 
wildfire, and undocumented immigration that alter the vegetation of 
occupied northern Mexican gartersnake habitat are documented throughout 
its range and reduce the habitat's suitability as cover for protection 
from predators, as a foraging area, and as an effective 
thermoregulatory site. However, Rorabaugh (2008, p. 26) suggests that 
an increased awareness of the potential for ecotourism to provide rural 
economic growth is occurring in many areas

[[Page 71806]]

within Sonora, Mexico, which may provide enhanced opportunities for 
conservation of biologically rich ecosystems in the future.
    Nonnative plant species, in particular shrubs (genus Tamarix) and 
buffelgrass, are increasing their distribution in both the United 
States and Mexico and adversely affect habitat suitability and 
availability for the northern Mexican gartersnake.

B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    The northern Mexican gartersnake may not be collected in the United 
States without special authorization by the Arizona Game and Fish 
Department or the New Mexico Department of Game and Fish. We have found 
no evidence that current or historical levels of lawful or unlawful 
field collecting of northern Mexican gartersnakes has played a 
significant role in the decline of this species. The Arizona Game and 
Fish Department recently produced identification cards for distribution 
that provide information to assist with the field identification of 
each of Arizona's five native gartersnake species, as well as guidance 
on submitting photographic vouchers for university museum collections. 
Additionally, Arizona State University and the University of Arizona 
recently began to accept photographic vouchers, versus physical 
specimens, in their respective museum collections, which will reduce 
the amount of collection. We believe these measures reduce the 
necessity for field biologists to collect physical specimens (unless 
discovered postmortem) for locality voucher purposes and, therefore, 
further reduce impacts to vulnerable populations of the northern 
Mexican gartersnake. We were unable to obtain information about the 
effect of overutilization for commercial, recreational, scientific, or 
educational purposes in Mexico. Specific discussion of the regulatory 
protections for the northern Mexican gartersnake is provided under 
Factor D ``Inadequacy of Existing Regulatory Mechanisms'' below.

C. Disease or Predation

    Disease. Disease in northern Mexican gartersnakes has not yet been 
documented as a specific threat in the United States or Mexico. 
However, because little is known about disease in wild snakes, it is 
premature to conclude that there is no disease threat that could 
directly affect remaining northern Mexican gartersnake populations 
(Rosen 2006).
    Disease and nonnative parasites have been implicated in the decline 
in the prey base of the northern Mexican gartersnake. Particularly, the 
outbreak of chytridiomycosis or ``Bd,'' a skin fungus (Batrachochytrium 
dendrobatidis), has been identified as a chief causative agent in the 
significant declines of many of the native ranid frogs and other 
amphibian species, and regional concerns exist for the native fish 
community due to nonnative parasites such as the Asian tapeworm 
(Bothriocephalus achelognathi) in southeastern Arizona (Rosen and 
Schwalbe 1997, pp. 14-15; 2002c, pp. 1-19; Morell 1999, pp. 728-732; 
Sredl and Caldwell 2000, p. 1; Hale 2001, pp. 32-37; Bradley et al. 
2002, p. 206). Bd has been implicated in both large-scale declines and 
local extirpations of many amphibians, chiefly anuran species, around 
the world (Johnson 2006, p. 3011). Lips et al. (2006, pp. 3166-3169) 
suggest that the high virulence and large number of potential hosts 
make Bd a serious threat to amphibian diversity. In Arizona, Bd 
infections have been reported in several northern Mexican gartersnake 
native prey species within the distribution of the snake (Morell 1999, 
pp. 731-732; Sredl and Caldwell 2000, p. 1; Hale 2001, pp. 32-37; 
Bradley et al. 2002, p. 207; USFWS 2002a, pp. 40802-40804; USFWS 2007, 
pp. 26, 29-32). Declines of native prey species of the northern Mexican 
gartersnake from Bd infections have contributed to the decline of this 
species in the United States and likely in Mexico (Morell 1999, pp. 
731-732; Sredl and Caldwell 2000, p. 1; Hale 2001, pp. 32-37; Bradley 
et al. 2002, p. 207; USFWS 2002a, pp. 40802-40804; USFWS 2007, pp. 26, 
29-32).
    Research shows that, in a pure culture, the fungus Batrachochytrium 
can grow on boiled snakeskin (keratin), which indicates the potential 
for the fungus to live on gartersnake skin in the wild, if other 
components of the ecosystem are favorable (Longcore et al. 1999, p. 
227). Despite the demonstrated potential, no reports of the organism on 
reptilian hosts in the wild have been documented. We, as well as other 
researchers, will monitor the incidence of this disease in gartersnakes 
in the wild for early detection purposes and to determine the status of 
this potential threat.
    Parasites have been observed in northern Mexican gartersnakes. 
Boyarski (2008b, pp. 5-6) recorded several snakes within the population 
at the Page Springs and Bubbling Ponds fish hatcheries with interior 
bumps or bulges along the anterior one-third of the body although the 
cause of these bumps was not identified or speculated upon, nor were 
there any signs of trauma to their body in these areas. Dr. Jim 
Jarchow, a veterinarian with herpetological expertise, reviewed 
photographs of affected specimens and suggested the bumps may likely 
contain plerocercoid larvae of a pseudophyllidean tapeworm (possibly 
Spirometra spp.), which are common in fish- and frog-eating 
gartersnakes. This may not be detrimental to their health provided the 
bumps do not grow large enough to impair movement or other bodily 
functions (Boyarski 2008b, p. 8). However, G[uacute]zman (2008, p. 102) 
documented the first observation of mortality of a Mexican gartersnake 
from a larval Eustrongylides sp. (endoparasitic nematode) which 
``raises the possibility that infection of Mexican gartersnakes by 
Eustrongylides sp. larvae might cause mortality in some wild 
populations,'' especially in the presence of other threats.
    Nonnative Species Interactions. A host of native predators prey 
upon northern Mexican gartersnakes including birds of prey, other 
snakes [kingsnakes (Lampropeltis sp.), whipsnakes (Masticophis sp.), 
etc.], wading birds, raccoons (Procyon lotor), skunks (Mephitis sp.), 
and coyotes (Canis latrans) (Rosen and Schwalbe 1988, p. 18). 
Historically, large, highly predatory native fish species such as 
Colorado pikeminnow may have preyed upon northern Mexican gartersnakes 
where the two species co-occurred. However, nonnative species represent 
the most serious threat to the northern Mexican gartersnake through 
direct predation and predation on northern Mexican gartersnake prey 
(competition). Nonnative species, such as the bullfrog, the northern 
(virile) crayfish (Orconectes virilis) and red swamp (Procambarus 
clarki) crayfish, and numerous species of nonnative sport and bait fish 
species continue to be the most significant threat to the northern 
Mexican gartersnake and to its prey base from direct predation, 
competition, and modification of habitat (Meffe 1985, pp. 179-185; 
Rosen and Schwalbe 1988, pp. 28, 32; 1997, p. 1; Bestgen and Propst 
1989, pp. 409-410; Clarkson and Rorabaugh 1989, pp. 531, 535; Marsh and 
Minckley 1990, p. 265; Stefferud and Stefferud 1994, p. 364; Douglas et 
al. 1994, pp. 9-19; Rosen et al. 1995, pp. 257-258; 1996b, pp. 2, 11-
13; 2001, p. 2; Degenhardt et al. 1996, p. 319; Fernandez and Rosen 
1996, pp. 8, 23-27; Richter et al. 1997, pp. 1089, 1092; Weedman and 
Young 1997, p. 1, Appendices B, C; Inman et al. 1998, p. 17; Rinne et 
al. 1998, pp. 4-6; Minckley

[[Page 71807]]

et al. 2002, p. 696; DFT 2003, p. 1; Clarkson et al. 2005, p. 20; Fagan 
et al. 2005, pp. 34, 34-41; Olden and Poff 2005, pp. 82-87; Turner 
2006, p. 10; Holycross et al. 2006, pp. 13-15; Brennan and Holycross 
2006, p. 123; USFWS 2007, pp. 22-23; Caldwell 2008a, 2008b; Jones 
2008b; d'Orgeix 2008; Haney et al. 2008, p. 59; Luja and 
Rodr[iacute]guez-Estrella 2008, pp.. 17-22; Rorabaugh 2008, p. 25; USFS 
2008; Wallace et al. 2008, pp. 243-244; Witte et al. 2008, p. 1).
    Riparian and aquatic communities in both the United States and 
Mexico have been dramatically impacted by a shift in species' 
composition, from being historically dominated by native fauna to being 
increasingly occupied by an expanding assemblage of nonnative animal 
species that have been intentionally or accidentally introduced, such 
as crayfish, bullfrogs, sportfish, and domestic pets. For example, in 
two of eight cases of northern Mexican gartersnake mortality collected 
at Bubbling Ponds Hatchery since 2006, the cause of death was 
considered to be from domestic cats (Boyarski 2008a).
    The population of northern Mexican gartersnakes at the hatcheries 
occurs with potential and known nonnative predators including rainbow 
and brown trout, largemouth and smallmouth bass, bluegill, crayfish (in 
Oak Creek), and bullfrogs (Boyarski 2008b, pp. 3-4, 8). Seven snakes 
(11 percent of those captured) were observed as having some level of 
tail damage, presumably from bullfrog predation attempts and were noted 
as having a lower body condition index (an indicator of overall health 
based on a set of pre-determined variables) (Boyarski 2008b, pp. 5, 8). 
The relatively low occurrence of tail damage, as compared to the 78 
percent of snakes with tail damage found by Rosen and Schwalbe (1988, 
pp. 28-31), may indicate (1) adequate vegetation density was used by 
gartersnakes to avoid bullfrog predation attempts; (2) a relatively low 
density population of bullfrogs occurs at the site (bullfrog population 
density data were not collected); (3) gartersnakes may not need to move 
significant distances to achieve foraging success, which might have 
reduced the potential for encounters with bullfrogs; or, (4) that 
gartersnakes infrequently escape bullfrog predation attempts, were 
removed from the population, and were consequently not detected by 
surveys. Additional information on tail damage as an indicator of 
predation is found in our discussion of Factor C below.
    Stock tanks associated with livestock grazing may facilitate the 
spread of nonnative species when nonnative species of fish, amphibians, 
and crayfish are intentionally or unintentionally stocked by anglers 
and private landowners (Rosen et al. 2001, p. 24). The management of 
stock tanks is an important consideration for northern Mexican 
gartersnakes. Stock tanks associated with livestock grazing can be 
intermediary ``stepping stones'' in the dispersal of nonnative species 
from larger source populations to new areas (Rosen et al. 2001, p. 24).
    The northern Mexican gartersnake appears to be particularly 
vulnerable to a loss in native prey species (Rosen and Schwalbe 1988, 
p. 20). Rosen et al. (2001, pp. 10, 13, 19) examined this issue in 
detail and proposed two reasons for the decline in northern Mexican 
gartersnakes following the loss or decline in the native prey base: (1) 
The species is unlikely to increase foraging efforts at the risk of 
increased predation; and (2) the species needs substantial food 
regularly to maintain its weight and health. If forced to forage more 
often for smaller prey items, a reduction in growth and reproductive 
rates can result (Rosen et al. 2001, pp. 10, 13). Rosen et al. (2001, 
p. 22) concluded that the presence and expansion of nonnative predators 
(mainly bullfrogs, crayfish, and green sunfish) are the primary causes 
of decline in northern Mexican gartersnakes and their prey in 
southeastern Arizona.
    The decline of the northern Mexican gartersnake within its 
historical and currently occurring distribution was subsequent to the 
declines in its prey base (native amphibian and fish populations) from 
predation following introductions of nonnative bullfrogs, crayfish, and 
numerous species of exotic sport and bait fish as documented in an 
extensive body of literature (Nickerson and Mays 1970, p. 495; Hulse 
1973, p. 278; Vitt and Ohmart 1978, p. 44; Meffe 1985, pp. 179-185; 
Ohmart et al. 1988, pp. 143-147; Rosen and Schwalbe 1988, pp. 28-31; 
1997, pp. 8-16; Bestgen and Propst 1989, pp. 409-410; Clarkson and 
Rorabaugh 1989, pp. 531-538; Marsh and Minckley 1990, p. 265; Sublette 
et al. 1990, pp. 112, 243, 246, 304, 313, 318; Stefferud and Stefferud 
1994, p. 364; Holm and Lowe 1995, p. 5; Rosen et al. 1995, pp. 251, 
257-258; 1996a, pp. 2-3; 1996b, p. 2; 2001, p. 2; Sredl et al. 1995a, 
pp. 7-8; 1995b, pp. 8-9; 1995c, pp. 7-8; 2000, p. 10; Degenhardt et al. 
1996, p. 319; Fernandez and Rosen 1996, pp. 8-27; Drost and Nowak 1997, 
p. 11; Weedman and Young 1997, p. 1, Appendices B, C; Inman et al. 
1998, p. 17; Rinne et al. 1998, pp. 4-6; Turner et al. 1999, p. 11; 
Nowak and Spille 2001, p. 11; Bonar et al. 2004, p. 3; Fagan et al. 
2005, pp. 34, 34-41; Olden and Poff 2005, pp. 82-87; Holycross et al. 
2006, pp. 13-15, 52-61; Brennan and Holycross 2006, p. 123; USFWS 2007, 
pp. 22-23; Caldwell 2008a, 2008b; Jones 2008b; d'Orgeix 2008; Haney et 
al. 2008, p. 59; Luja and Rodr[iacute]guez-Estrella 2008, pp. 17-22; 
Rorabaugh 2008, p. 25; USFS 2008; Wallace et al. 2008, pp. 243-244; 
Witte et al. 2008, p. 1).
    Declines in the Northern Mexican Gartersnake Anuran Prey Base. 
Declines in the native leopard frog populations in Arizona have 
contributed to declines in the northern Mexican gartersnake as a 
primary native predator. Native ranid frog species such as lowland 
leopard frogs, northern leopard frogs, and federally threatened 
Chiricahua leopard frogs have all experienced significant declines 
throughout their distribution in the Southwest, partially due to 
predation and competition with nonnative species (Clarkson and 
Rorabaugh 1989, pp. 531, 535; Hayes and Jennings 1986, p. 490). Rosen 
et al. (1995, pp. 257-258) found that Chiricahua leopard frog 
distribution in the Chiricahua Mountain region of Arizona was inversely 
related to nonnative species distribution and without corrective 
action, predicted that the Chiricahua leopard frog will be extirpated 
from this region. Along the Mogollon Rim, Holycross et al. (2006, p. 
13) found that only 8 sites of 57 surveyed (15 percent) consisted of an 
entirely native anuran community and that native frog populations in 
another 19 sites (33 percent) had been completely displaced by invading 
bullfrogs.
    Scotia Canyon in the Huachuca Mountains of southeastern Arizona is 
a location where corresponding declines of leopard frog and northern 
Mexican gartersnake populations have been documented through repeated 
survey efforts over time (Holm and Lowe 1995, p. 33). Surveys of Scotia 
Canyon occurred during the early 1980s and again during the early 
1990s. Leopard frogs in Scotia Canyon were infrequently observed during 
the early 1980s and were apparently extirpated by the early 1990s (Holm 
and Lowe 1995, pp. 45-46). Northern Mexican gartersnakes were observed 
in decline during the early 1980s with low capture rates remaining 
through the early 1990s (Holm and Lowe 1995, pp. 27-35). Surveys 
documented further decline in 2000 (Rosen et al. 2001, pp. 15-16). A 
former large, local population of northern Mexican gartersnakes at the 
San Bernardino National Wildlife Refuge has also experienced a 
correlative decline of leopard frog and northern Mexican gartersnake

[[Page 71808]]

populations, at least in part related to illegal immigration and 
smuggling activities in riparian and aquatic habitats as discussed in 
Factor A above (Rosen and Schwalbe 1988, p. 28; 1995, p. 452; 1996, pp. 
1-3; 1997, p. 1; 2002b, pp. 223-227; 2002c, pp. 31, 70; Rosen et al. 
1996b, pp. 8-9; 2001, pp. 6-10). Survey data indicate that declines of 
leopard frog populations, often correlated with nonnative species 
introductions, the spread of chytridiomycosis disease, and habitat 
modification and destruction, have occurred throughout much of the U.S. 
distribution of the northern Mexican gartersnake (Nickerson and Mays 
1970, p. 495; Vitt and Ohmart 1978, p. 44; Ohmart et al. 1988, p. 150; 
Rosen and Schwalbe 1988, Appendix I; 1995, p. 452; 1996, pp. 1-3; 1997, 
p. 1; 2002b, pp. 232-238; 2002c, pp. 1, 31; Clarkson and Rorabaugh 
1989, pp. 531-538; Sredl et al. 1995a, pp. 7-8; 1995b, pp. 8-9; 1995c, 
pp. 7-8; 2000, p. 10; Holm and Lowe 1995, pp. 45-46; Rosen et al. 
1996b, p. 2; 2001, pp. 2, 22; Degenhardt et al. 1996, p. 319; Fernandez 
and Rosen 1996, pp. 6-20; Drost and Nowak 1997, p. 11; Turner et al. 
1999, p. 11; Nowak and Spille 2001, p. 32; Holycross et al. 2006, pp. 
13-14, 52-61). Specifically, Holycross et al. (2006, pp. 53-57, 59) 
recently documented extirpations of the northern Mexican gartersnake's 
native leopard frog prey base at several currently, historically, or 
potentially occupied locations including the Agua Fria River in the 
vicinity of Table Mesa Road and Little Grand Canyon Ranch and at Rock 
Springs, Dry Creek from Dugas Road to Little Ash Creek, Little Ash 
Creek from Brown Spring to Dry Creek, Sycamore Creek (Agua Fria 
watershed) in the vicinity of the Forest Service Cabin, at the Page 
Springs and Bubbling Ponds fish hatchery along Oak Creek, Sycamore 
Creek (Verde River watershed) in the vicinity of the confluence with 
the Verde River north of Clarkdale, along several reaches of the Verde 
River mainstem, Cherry Creek on the east side of the Sierra Ancha 
Mountains, and Tonto Creek from Gisela to ``the Box,'' near its 
confluence with Rye Creek.
    Rosen et al. (2001, p. 22) identified the expansion of bullfrogs 
into the Sonoita grasslands, which border occupied northern Mexican 
gartersnake habitat, and the introduction of crayfish into Lewis 
Springs as being of particular concern in terms of future recovery 
efforts for the northern Mexican gartersnake. Rosen et al. (1995, pp. 
252-253) sampled 103 sites in the Chiricahua Mountains region, which 
included the Chiricahua, Dragoon, and Peloncillo mountains, and the 
Sulphur Springs, San Bernardino, and San Simon valleys. They found that 
43 percent of all cold-blooded aquatic and semi-aquatic vertebrate 
species detected were nonnative. The most commonly encountered 
nonnative species was the bullfrog (Rosen et al. 1995, p. 254).
    Native ranid frogs (particularly lowland and Chiricahua leopard 
frogs), which are a primary prey species for northern Mexican 
gartersnakes, are one of the most imperiled taxa of Sonora, Mexico, due 
primarily to threats from nonnative species (bullfrogs, crayfish, and 
sport fish) (Rorabaugh 2008, p. 25).
    Witte et al. (2008, p. 1) found that the disappearance of ranid 
frog populations in Arizona were 2.6 times more likely in the presence 
of crayfish. Witte et al. (2008, p. 7) emphasized the significant 
influence of nonnative species on the disappearance of ranid frogs in 
Arizona.
    Declines in the Northern Mexican Gartersnake Native Fish Prey Base. 
Native fish species such as the federally endangered Gila chub, 
roundtail chub (a species petitioned for Federal listing), and 
federally endangered Gila topminnow historically were among the primary 
prey species for the northern Mexican gartersnake (Rosen and Schwalbe 
1988, p. 18). Northern Mexican gartersnakes depend on native fish as a 
principle part of their prey base, although nonnative mosquitofish may 
also be taken as prey (Holycross et al. 2006, p. 23). Both nonnative 
sport and bait fish compete with the northern Mexican gartersnake in 
terms of its native fish and native anuran prey base. Collier et al. 
(1996, p. 16) note that interactions between native and nonnative fish 
have significantly contributed to the decline of many native fish 
species from direct predation and indirectly from competition (which 
has adversely affected the prey base for northern Mexican 
gartersnakes). Holycross et al. (2006, pp. 53-55) recently documented 
significantly depressed or extirpated native fish prey bases for the 
northern Mexican gartersnake along the Agua Fria in the vicinity of 
Table Mesa Road and the Little Grand Canyon Ranch, along Dry Creek from 
Dugas Road to Little Ash Creek, along Little Ash Creek from Brown 
Spring to Dry Creek, along Sycamore Creek (Agua Fria watershed) in the 
vicinity of the Forest Service Cabin, and along Sycamore Creek (Verde 
River watershed) in the vicinity of its confluence with the Verde River 
north of Clarkdale. Rosen et al. (2001, Appendix I) documented the 
decline of several native fish species in several locations visited in 
southeastern Arizona, further affecting the prey base of northern 
Mexican gartersnakes in that area.
    The widespread decline of native fish species from the arid 
southwestern United States and Mexico has resulted largely from 
interactions with nonnative species and has been captured in the 
listing rules of 13 native species listed under the Act whose 
historical ranges overlap with the historical distribution of the 
northern Mexican gartersnake. Native fish species that were likely prey 
species for the northern Mexican gartersnake, including bonytail chub 
(Gila elegans, 45 FR 27710, April 23, 1980), Yaqui catfish (Ictalurus 
pricei, 49 FR 34490, August 31, 1984), Yaqui chub (Gila purpurea, 49 FR 
34490, August 31, 1984), Yaqui topminnow (Poeciliopsis occidentalis 
sonoriensis, 32 FR 4001, March 11, 1967), beautiful shiner (Cyprinella 
formosa, 49 FR 34490, August 31, 1984), humpback chub (Gila cypha, 32 
FR 4001, March 11, 1967), Gila chub (Gila intermedia, 70 FR 66663, 
November 2, 2005), Colorado pikeminnow (Ptychocheilus lucius, 32 FR 
4001, March 11, 1967), spikedace (Meda fulgida, 51 FR 23769, July 1, 
1986) loach minnow (Tiaroga cobitis, 51 FR 39468, October 28, 1986), 
razorback sucker (Xyrauchen texanus, 56 FR 54957, October 23, 1991), 
desert pupfish (Cyprinodon macularius, 51 FR 10842, March 31, 1986), 
and Gila topminnow (Poeciliopsis occidentalis occidentalis, 32 FR 4001, 
March 11, 1967). In total within Arizona, 19 of 31 (61 percent) of 
native fish species are listed under the Act. Arizona ranks the highest 
of all 50 States in the percentage of native fish species with 
declining trends (85.7 percent, Stein 2002, p. 21; Warren and Burr 
1994, pp. 6-18).
    There are significant ongoing threats from nonnative species to the 
snake in Mexico. Lyons and Navarro-Perez (1990, pp. 32-46) investigated 
the fish communities of 17 streams in and adjacent to the Sierra de 
Manantl[aacute]n Biosphere Reserve in Jalisco and Colima, Mexico. They 
noted the exceptionally high number of native fish species with small, 
localized distributions, which makes them more susceptible to threats 
and subsequent extirpation, stating that degradation of just a few 
streams could result in the elimination of many species of fish and, 
thus, prey availability for the northern Mexican gartersnake.
    In an evolutionary context, native fishes co-evolved with very few 
predatory fish species, whereas many of the nonnative species co-
evolved with many predatory species (Clarkson et al. 2005, p. 21). A 
contributing factor to the decline of native fish species cited by 
Clarkson et al. (2005, p. 21) is that most

[[Page 71809]]

of the nonnative species evolved behaviors, such as nest guarding, to 
protect their offspring from these many predators, while native species 
are generally broadcast spawners that provide no parental care. In the 
presence of nonnative species, the reproductive behaviors of native 
fish fail to allow them to compete effectively with the nonnative 
species and, as a result, the viability of native fish populations is 
reduced.
    Olden and Poff (2005, p. 75) stated that environmental degradation 
and the proliferation of nonnative fish species threaten the highly 
localized and unique fish faunas of the American Southwest. The fastest 
expanding nonnative species are red shiner (Cyprinella lutrensis), 
fathead minnow (Pimephales promelas), green sunfish (Lepomis 
cyanellus), largemouth bass (Micropterus salmoides), western 
mosquitofish, and channel catfish (Ictalurus punctatus). These species 
are considered to be the most invasive in terms of their negative 
impacts on native fish communities (Olden and Poff 2005, p. 75). Many 
nonnative fishes in addition to those listed immediately above, 
including yellow and black bullheads (Ameiurus sp.), flathead catfish 
(Pylodictis olivaris), and smallmouth bass (Micropterus dolomieue), 
have been introduced into formerly and currently occupied northern 
Mexican gartersnake habitat and are predators on northern Mexican 
gartersnakes and their prey (Bestgen and Propst 1989, pp. 409-410; 
Marsh and Minckley 1990, p. 265; Sublette et al. 1990, pp. 112, 243, 
246, 304, 313, 318; Abarca and Weedman 1993, pp. 6-12; Stefferud and 
Stefferud 1994, p. 364; Weedman and Young 1997, pp. 1, Appendices B, C; 
Rinne et al. 1998, pp. 3-6; Voeltz 2002, p. 88; Bonar et al. 2004, pp. 
1-108; Fagan et al. 2005, pp. 34, 38-39, 41).
    Several authors have identified both the presence of nonnative fish 
as well as their deleterious effects on native species within Arizona. 
Abarca and Weedman (1993, pp. 6-12) found that the number of nonnative 
fish species was twice the number of native fish species in Tonto Creek 
in the early 1990s, with a stronger nonnative species influence in the 
lower reaches where the northern Mexican gartersnake is considered to 
still occur. Surveys in the Salt River above Lake Roosevelt indicate a 
decline of roundtail chub and other natives with an increase in 
flathead and channel catfish numbers (Voeltz 2002, p. 49). In New 
Mexico, nonnative fish have been identified as the main cause for 
declines observed in roundtail chub populations (Voeltz 2002, p. 40). 
Douglas et al. (1994, pp. 9-19) provide data indicating that the 
nonnative red shiner may be competitively displacing spikedace (a 
potential prey item of the northern Mexican gartersnake) in Arizona and 
New Mexico within the historical or current distribution of the 
northern Mexican gartersnake.
    In a comprehensive and thorough assessment of the Verde River, 
Bonar et al. (2004, p. 57) found that in the Verde River mainstem, 
nonnative fishes were approximately 2.6 times more dense per unit 
volume of river than native fishes, and their populations were 
approximately 2.8 times that of native fishes per unit volume of river.
    Haney et al. (2008, p. 61) declared the northern Mexican 
gartersnake as nearly lost from the Verde River and suggested that 
diminished river flow may be an important factor. Differing river flows 
may provide both advantages and disadvantages to aquatic species. The 
timing, duration, intensity, and frequency of flood events has been 
altered to varying degrees by the presence of dams along the Verde 
River, which has an effect on fish communities. Specifically, Haney et 
al. (2008, p. 61) suggested that flood pulses may help to reduce 
populations of nonnative species (see discussion below) and efforts to 
increase the baseflows may assist in sustaining native prey species for 
the northern Mexican gartersnake. However, the investigators also 
suggest that, because the northern Mexican gartersnake preys on both 
fish and frogs, it may be less affected by reductions in baseflow but 
might incur greater risks from concentrating nonnative predators and 
higher water-borne disease rates (Haney et al. 2008, pp. 82, 93).
    The Desert Fishes Team (DFT) is an ``independent group of 
biologists and parties interested in protecting and conserving native 
fishes of the Colorado River basin'' and includes personnel from the 
U.S. Forest Service, U.S. Bureau of Reclamation, U.S. Bureau of Land 
Management, University of Arizona, Arizona State University, the Nature 
Conservancy, and independent experts (DFT 2003, p. 1). DFT (2003, p. 1) 
declared the native fish fauna of the Gila River basin to be critically 
imperiled, cite habitat destruction and nonnative species as the 
primary factors for the declines, and call for the control and removal 
of nonnative fish as an overriding need to prevent the decline and 
ultimate extinction of native fish species within the basin.
    Northern Mexican gartersnakes can successfully use some nonnative 
species, such as mosquitofish and red shiner, as prey species. However, 
all other nonnative species, most notably the spiny-rayed fish, are not 
considered prey species for the northern Mexican gartersnake. These 
nonnative species can be difficult to swallow due to their body shape 
and spiny dorsal fins. They are predatory on juvenile gartersnakes and 
reduce the abundance of or completely eliminate native fish 
populations. This is particularly important in the wake of random, 
high-intensity events, such as flooding, extreme water temperatures, or 
excessive turbidity. Native fish are adapted to the dramatic 
fluctuations in water conditions and flow regimes, and generally 
persist in the wake of stochastic events and continue to provide a prey 
base for the northern Mexican gartersnake. Nonnative fish, even species 
that may be used as prey by the northern Mexican gartersnake, generally 
are ill-adapted to these conditions and may be removed from the area 
temporarily or permanently, depending on the hydrologic connectivity to 
current populations. If an area is solely comprised of nonnative fish, 
the northern Mexican gartersnake may be faced with nutritional stress 
or starvation because only a few small-bodied, soft-rayed fish species 
are taken as prey and significant effort may be required to obtain 
these species.
    Clarkson et al. (2005) discuss management conflicts as a primary 
factor in the decline of native fish species in the southwestern United 
States and declare the entire native fauna as imperiled. The 
investigators cite nonnative species as the most consequential factor 
that has led to rangewide declines that prevents or negates species' 
recovery efforts from being implemented or being successful (Clarkson 
et al. 2005, p. 20). Clarkson et al. (2005, p. 20) note that over 50 
nonnative species have been introduced into the Southwest as either 
sportfish or baitfish and are still being actively stocked, managed 
for, and promoted by both Federal and State agencies as nonnative 
recreational fisheries. To help resolve the conflicting management 
mandates of native fish recovery and the promotion of recreational 
fisheries, Clarkson et al. (2005, pp. 22-25) propose the designation of 
entire watersheds as having either native or nonnative fisheries and 
manage for these goals aggressively. While some discussion within 
Arizona has taken place to designate portions of watersheds as either 
native or nonnative fisheries, the geographic areas under consideration 
for native fishery development do not currently coincide with current 
populations of northern Mexican gartersnakes and no immediate

[[Page 71810]]

benefit is provided to the subspecies from their implementation. 
Clarkson et al. (2005, p. 25) suggest that current management of 
fisheries within the southwestern United States as status quo will have 
serious adverse effects to native fish species and affect the long-term 
viability of the northern Mexican gartersnake and to its potential 
recovery.
    We are not aware of any studies that have addressed the direct 
relationship between prey base diversity and northern Mexican 
gartersnake recruitment and survivorship. However, Krause and Burghardt 
(2001, pp. 100-123) discuss the benefits and costs that may be 
associated with diet variability in the common gartersnake (Thamnophis 
sirtalis), an ecologically similar species to the northern Mexican 
gartersnake. Foraging for mixed-prey species may impede predator 
learning, as compared to specialization, on a certain prey species, but 
may also provide long-term benefits (Krause and Burghardt 2001, p. 
101). Krause and Burghardt (2001, p. 112) stated that varied predatory 
experience played an important role in the feeding abilities of 
gartersnakes through the first 8 months of age. These data suggest that 
a varied prey base might also be important for neonatal and juvenile 
northern Mexican gartersnakes (also a species with a varied diet) and 
that decreases in the diversity of the prey base during the young age 
classes might adversely affect the ability of individuals to capture 
prey throughout their lifespan, in addition to the more obvious effects 
of reduced prey availability.
    The most conclusive evidence for the northern Mexican gartersnake's 
intolerance for nonnative fish invasions remains the fact that, in most 
incidences, nonnative fish species generally do not occur in the same 
locations as the northern Mexican gartersnake and its native prey 
species. Additional information on the decline of the northern Mexican 
gartersnake's native fish prey species can be found in Bonar et al. 
(2004, pp. 4, 79-87); DFT (2003, pp. 1-3, 5-6, 19; 2004, pp. 1-2, 4-5, 
10, Table 1; 2006, pp. iii, 25); Richter et al. (1997, pp. 1081-1093); 
and Haney et al. (2008, pp. 54-61, 82, 93).
    Bullfrog Diet and Distribution. Bullfrogs are widely considered one 
of the most serious threats to the northern Mexican gartersnake 
throughout its range (Conant 1974, pp. 471, 487-489; Rosen and Schwalbe 
1988, pp. 28-30; Rosen et al. 2001, pp. 21-22). Bullfrogs adversely 
affect northern Mexican gartersnakes through direct predation of 
juveniles and sub-adults and from competition with native prey species. 
Bullfrogs first appeared in Arizona in 1926, as a result of a 
systematic introduction effort by the State Game Department (now, the 
Arizona Game and Fish Department) for the purposes of sport hunting and 
as a food source. (Tellman 2002, p. 43). Bullfrogs are extremely 
prolific, adept at colonizing new areas, and may disperse to distances 
of 6.8 miles (10.9 km) and likely further within drainages (Bautista 
2002, p. 131; Rosen and Schwalbe 2002a, p. 7; Casper and Hendricks 
2005, p. 582). In Arizona, using mark and recapture methods, bullfrogs 
have been documented to make overland movements of up to 7 miles (11 
kilometers) across semi-desert grassland habitat on the Buenos Aires 
National Wildlife Refuge (BANWR) (Suhre 2008). Investigators on the 
BANWR also observed two bullfrogs at an overland distance of 10 miles 
(16 kilometers) from the nearest source population although the origin 
of the bullfrogs could not be confirmed. Batista (2002, p. 131) 
confirmed ``the strong colonizing skills of the bullfrog and that the 
introduction of this exotic species can disturb local anuran 
communities.''
    Bullfrogs are voracious, opportunistic, even cannibalistic 
predators that readily attempt to consume any animal smaller than 
themselves, including other species within the same genus, which can 
comprise 80 percent of their diet (Casper and Hendricks 2005, p. 543). 
Bullfrogs have a varied diet, which has been documented to include 
vegetation, numerous invertebrate and vertebrate species which include 
numerous species of snakes [eight genera; including six different 
species of gartersnakes, two species of rattlesnakes, and Sonoran 
gophersnakes (Pituophis catenifer affinis)] (Bury and Whelan 1984, p. 
5; Clarkson and DeVos 1986, p. 45; Holm and Lowe 1995, pp. 37-38; 
Carpenter et al. 2002, p. 130; King et al. 2002; Hovey and Bergen 2003, 
pp. 360-361; Casper and Hendricks 2005, p. 544; Combs et al. 2005, p. 
439; Wilcox 2005, p. 306; DaSilva et al. 2007, p. 443; Neils and Bugbee 
2007, p. 443).
    Bullfrogs have been documented throughout the State of Arizona. 
Holycross et al. (2006, pp. 13-14, 52-61) found bullfrogs at 55 percent 
of sample sites in the Agua Fria watershed, 62 percent of sites in the 
Verde River watershed, 25 percent of sites in the Salt River watershed, 
and 22 percent of sites in the Gila River watershed. In total, 
bullfrogs were observed at 22 of the 57 sites surveyed (39 percent) 
across the Mogollon Rim (Holycross et al. 2006, p. 13). A number of 
authors have also documented the presence of bullfrogs through their 
survey efforts throughout Arizona in specific regional areas, 
drainages, and disassociated wetlands within or adjacent to the 
historical distribution of the northern Mexican gartersnake, including 
the Kaibab National Forest (Sredl et al. 1995a, p. 7); the Coconino 
National Forest (Sredl et al. 1995c, p. 7); the White Mountain Apache 
Reservation (Hulse 1973, p. 278); Beaver Creek (tributary to the Verde 
River) (Drost and Nowak 1997, p. 11); the Watson Woods Riparian 
Preserve near Prescott (Nowak and Spille 2001, p. 11); the Tonto 
National Forest (Sredl et al. 1995b, p. 9); the Lower Colorado River 
(Vitt and Ohmart 1978, p. 44; Clarkson and DeVos 1986, pp. 42-49; 
Ohmart et al. 1988, p. 143); the Huachuca Mountains (Rosen and Schwalbe 
1988, Appendix I; Holm and Lowe 1995, pp. 27-35; Sredl et al. 2000, p. 
10; Rosen et al. 2001, Appendix I); the Pinaleno Mountains region 
(Nickerson and Mays 1970, p. 495); the San Bernardino National Wildlife 
Refuge (Rosen and Schwalbe 1988, Appendix I; 1995, p. 452; 1996, pp. 1-
3; 1997, p. 1; 2002b, pp. 223-227; 2002c, pp. 31, 70; Rosen et al. 
1995, p. 254; 1996b, pp. 8-9; 2001, Appendix I); the Buenos Aires 
National Wildlife Refuge (Rosen and Schwalbe 1988, Appendix I); the 
Arivaca Area (Rosen and Schwalbe 1988, Appendix I; Rosen et al. 2001, 
Appendix I); Cienega Creek drainage (Rosen et al. 2001, Appendix I); 
Babocamari River drainage (Rosen et al. 2001, Appendix I); Turkey Creek 
drainage (Rosen et al. 2001, Appendix I); O'Donnell Creek drainage 
(Rosen et al. 2001, Appendix I); Appleton-Whittell Research Ranch near 
Elgin (Rosen et al. 2001, Appendix I); Santa Cruz River drainage (Rosen 
and Schwalbe 1988, Appendix I; Rosen et al. 2001, Appendix I); San 
Rafael Valley (Rosen et al. 2001, Appendix I); San Pedro River drainage 
(Rosen and Schwalbe 1988, Appendix I; Rosen et al. 2001, Appendix I); 
Bingham Cienega (Rosen et al. 2001, Appendix I); Sulfur Springs Valley 
(Rosen et al. 1996a, pp. 16-17); Whetstone Mountains region (Turner et 
al. 1999, p. 11); Aqua Fria River drainage (Rosen and Schwalbe 1988, 
Appendix I; Holycross et al. 2006, pp. 13, 15-18, 52-53); Verde River 
drainage (Rosen and Schwalbe 1988, Appendix I; Holycross et al. 2006, 
pp. 13, 26-28, 55-56); greater metropolitan Phoenix area (Rosen and 
Schwalbe 1988, Appendix I); greater metropolitan Tucson area (Rosen and 
Schwalbe 1988, Appendix I); Sonoita Creek drainage (Rosen and Schwalbe 
1988, Appendix I); Sonoita Grasslands (Rosen and Schwalbe 1988, 
Appendix I); Canelo Hills (Rosen and Schwalbe 1988,

[[Page 71811]]

Appendix I); Pajarito Mountains (pers. observation, J. Servoss, Fish 
and Wildlife Biologist, U.S. Fish and Wildlife Service); Picacho 
Reservoir (Rosen and Schwalbe 1988, Appendix I); Dry Creek drainage 
(Holycross et al. 2006, pp. 19, 53); Little Ash Creek drainage 
(Holycross et al. 2006, pp. 19, 54); Oak Creek drainage (Holycross et 
al. 2006, pp. 23, 54); Sycamore Creek drainages (Holycross et al. 2006, 
pp. 20, 25, 54-55); Rye Creek drainage (Holycross et al. 2006, pp. 37, 
58); Spring Creek drainage (Holycross et al. 2006, pp. 25, 59); Tonto 
Creek drainage (Holycross et al. 2006, pp. 40-44, 59; Wallace et al. 
2008, pp. 243-244); San Francisco River drainage (Holycross et al. 
2006, pp. 49-50, 61); Sonoita Creek (Tuner 2006; p. 10); and the upper 
Gila River drainage (Holycross et al. 2006, pp. 45-50, 60-61).
    Perhaps one of the most serious consequences of bullfrog 
introductions is their persistence in an area once they have become 
established, and the subsequent difficulty in eliminating bullfrog 
populations. Rosen and Schwalbe (1995, p. 452) experimented with 
bullfrog removal at various sites on the San Bernardino National 
Wildlife Refuge in addition to a control site with no bullfrog removal 
in similar habitat on the BANWR. Removal of adult bullfrogs, without 
removal of eggs and tadpoles, resulted in a substantial increase in 
younger age-class bullfrogs where removal efforts were the most 
intensive (Rosen and Schwalbe 1997, p. 6). Contradictory to the goals 
of bullfrog eradication, evidence from dissection samples from young 
adult and sub-adult bullfrogs indicated these age-classes readily prey 
upon juvenile bullfrogs (up to the average adult leopard frog size) as 
well as juvenile gartersnakes, which suggests that the selective 
removal of only the large adult bullfrogs (presumed to be the most 
dangerous size class to leopard frogs and gartersnakes), favoring the 
young adult and sub-adult age classes, could indirectly lead to 
increased predation of leopard frogs and juvenile gartersnakes (Rosen 
and Schwalbe 1997, p. 6). These findings illustrate that in addition to 
large adults, bullfrogs in the young adult and subadult age classes 
also negatively impact northern Mexican gartersnakes and their prey 
species.
    Bullfrog Effects on the Native Anuran Prey Base for the Northern 
Mexican Gartersnake. As documented above and in the following studies, 
bullfrogs significantly reduce native anuran prey availability for the 
northern Mexican gartersnake (Conant (1974, pp. 471, 487-489); Hayes 
and Jennings (1986, pp. 491-492); Rosen and Schwalbe (1988, pp. 28-30; 
2002b, pp. 232-238); Rosen et al. (1995, pp. 257-258; 2001, pp. 2, 
Appendix I); Wu et al. (2005, p. 668); Pearl et al. (2004, p. 18); 
Kupferberg (1994, p. 95) Kupferburg (1997, pp. 1736-1751); Lawler et 
al. (1999); Bury and Whelan (1986, pp. 9-10); Hayes and Jennings (1986, 
pp. 500-501); Moyle (1973, pp. 18-22)). Different age classes of 
bullfrogs within a community can affect native ranid populations via 
different mechanisms. Juvenile bullfrogs affect native ranids through 
competition, male bullfrogs affect native ranids through predation, and 
female bullfrogs affect native ranids through both mechanisms depending 
on body size and microhabitat (Wu et al. 2005, p. 668). Pearl et al. 
(2004, p. 18) also suggested that the effect of bullfrog introductions 
on native ranids may be different based on specific habitat conditions, 
but also suggested that an individual ranid frog species' physical 
ability to escape influences the effect of bullfrogs on each native 
ranid community.
    Bullfrog Predation on Northern Mexican Gartersnakes. Sub-adult and 
adult bullfrogs not only compete with the northern Mexican gartersnake 
for prey items, but directly prey upon juvenile and occasionally sub-
adult northern Mexican gartersnakes (Rosen and Schwalbe 1988, pp. 28-
31; 1995, p. 452; 2002b, pp. 223-227; Holm and Lowe 1995, pp. 29-29; 
Rossman et al. 1996, p. 177; AGFD In Prep, p. 12; 2001, p. 3; Rosen et 
al. 2001, pp. 10, 21-22; Carpenter et al. 2002, p. 130; Wallace 2002, 
p. 116). A well-circulated photograph of an adult bullfrog in the 
process of consuming a northern Mexican gartersnake at Parker Canyon 
Lake, Cochise County, Arizona, taken by John Carr of the Arizona Game 
and Fish Department in 1964, provides photographic documentation of 
bullfrog predation (Rosen and Schwalbe 1988, p. 29; 1995, p. 452). A 
common observation in northern Mexican gartersnake populations that co-
occur with bullfrogs is a preponderance of large, mature adult snakes 
with conspicuously low numbers of individuals in the newborn and 
juvenile age size classes due to bullfrogs preying on young small 
snakes, which ultimately leads to low reproductive rates and survival 
of young (Rosen and Schwalbe 1988, p. 18; Holm and Lowe 1995, p. 34). 
Potential recruitment problems for northern Mexican gartersnakes due to 
effects from nonnative species are also suspected at Tonto Creek 
(Wallace et al. 2008, pp. 243-244).
    The tails of gartersnakes broken off through predation attempts may 
also lead to infection or compromise an individual's physical ability 
to escape future predation attempts or successfully forage. Tails of 
gartersnakes do not regenerate. The incidence of tail breaks in 
gartersnakes can often be used to assess predation pressures within 
gartersnake populations. Rosen and Schwalbe (1988, p. 22) found the 
incidence of tail breaks to be statistically higher in females than in 
males. Fitch (2003, p. 212) also found that tail breaks in the common 
gartersnake occurred more frequently in females than males and in 
adults more than in juveniles. Fitch (2003, p. 212) also commented 
that, while tail breakage in gartersnakes can save the life of an 
individual snake, it also leads to permanent handicapping of the snake, 
resulting in slower swimming and crawling speeds, which could leave the 
snake more vulnerable to predation or affect its foraging ability. 
Furthermore, Mushinsky and Miller (1993, pp. 662-664) found that the 
incidence of tail injury in water snakes in the genera Nerodia and 
Regina (which have similar life histories to northern Mexican 
gartersnakes) was higher in females than in males and in adults more 
than juveniles. This can be explained by higher basking rates 
associated with pregnant females that increase their visibility to 
predators. Additionally, predation on juvenile snakes generally results 
in complete consumption of the animal, which would limit observations 
of tail injury in their age class. Rosen and Schwalbe (1988, p. 22) 
suggested that the indication that female northern Mexican gartersnakes 
bear more injuries is consistent with the inference that they employ a 
riskier foraging strategy. Willis et al. (1982, p. 98) discussed the 
incidence of tail injury in three species in the genus Thamnophis 
(common gartersnake, Butler's gartersnake (T. butleri), and the eastern 
ribbon snake (T. sauritus)) and concluded that individuals that 
suffered nonfatal injuries prior to reaching a length of 12 in (30 cm) 
are not likely to survive and that physiological stress during post-
injury hibernation may play an important role in subsequent mortality.
    Ecologically significant observations on tail injuries were made by 
Rosen and Schwalbe (1988, pp. 28-31) on the formerly occurring 
population of northern Mexican gartersnakes on the San Bernardino 
National Wildlife Refuge. Seventy-eight percent of specimens had broken 
tails with a ``soft and club-like'' terminus, which suggests repeated 
injury from multiple predation attempts by bullfrogs. While medically

[[Page 71812]]

examining pregnant female northern Mexican gartersnakes, Rosen and 
Schwalbe (1988, p. 28) noted bleeding from the posterior region which, 
suggested to the investigators the snakes suffered from ``squeeze-
type'' injuries inflicted by adult bullfrogs. While a sub-adult or 
adult northern Mexican gartersnake may survive an individual predation 
attempt from a bullfrog while only incurring tail damage, secondary 
effects from infection of the wound can significantly contribute to 
mortality of individuals.
    Research on the effects of attempted predation performed by 
Mushinsky and Miller (1993, pp. 661-664) and Willis et al. (1982, pp. 
100-101) supports the observations made by Holm and Lowe (1995, p. 34) 
on the northern Mexican gartersnake population age class structure in 
Scotia Canyon in the Huachuca Mountains of southeastern Arizona in the 
early 1990s. Specifically, Holm and Lowe (1995, pp. 33-34) observed a 
conspicuously greater number of adult snakes in that population than 
sub-adult snakes, as well as a higher incidence of tail injury (89 
percent) in all snakes captured. Bullfrogs have been identified as the 
primary cause for both the collapse of the native leopard frog (prey 
base for the northern Mexican gartersnake) and northern Mexican 
gartersnake populations on the San Bernardino National Wildlife Refuge 
(Rosen and Schwalbe 1988, p. 28; 1995, p. 452; 1996, pp. 1-3; 1997, p. 
1; 2002b, pp. 223-227; 2002c, pp. 31, 70; Rosen et al. 1996b, pp. 8-9). 
Rosen and Schwalbe (1988, p. 18) stated that the low survivorship of 
newborns, and possibly yearlings, due to bullfrog predation is an 
important proximate cause of population declines of this snake at the 
San Bernardino National Wildlife Refuge and throughout its distribution 
in Arizona.
    Crayfish. Nonnative crayfish are a primary threat to many prey 
species of the northern Mexican gartersnake and may also prey upon 
juvenile gartersnakes (Fernandez and Rosen 1996, p. 25; Voeltz 2002, 
pp. 87-88; USFWS 2007, p. 22). Fernandez and Rosen (1996, p. 3) studied 
the effects of crayfish introductions on two stream communities in 
Arizona, a low-elevation semi-desert stream and a high mountain stream, 
and concluded that crayfish can noticeably reduce species diversity and 
destabilize food chains in riparian and aquatic ecosystems through 
their effect on vegetative structure, stream substrate (stream bottom; 
i.e., silt, sand, cobble, boulder) composition, and predation on eggs, 
larval, and adult forms of native invertebrate and vertebrate species. 
Crayfish fed on embryos, tadpoles, newly metamorphosed frogs, and adult 
leopard frogs, but they did not feed on egg masses (Fernandez and Rosen 
1996, p. 25). However, Gamradt and Kats (1996, p. 1155) found that 
crayfish readily consumed the egg masses of California newts (Taricha 
torosa). Fernandez and Rosen (1996, pp. 6-19, 52-56) and Rosen (1987, 
p. 5) discussed observations of inverse relationships between crayfish 
abundance and native reptile and amphibian populations including 
narrow-headed gartersnakes, northern leopard frogs, and Chiricahua 
leopard frogs. Crayfish may also affect native fish populations. 
Carpenter (2005, pp. 338-340) documented that crayfish may reduce the 
growth rates of native fish through competition for food and noted that 
the significance of this impact may vary between species. Crayfish also 
prey on fish eggs and larvae (Inman et al. 1998, p. 17).
    Crayfish alter the abundance and structure of aquatic vegetation by 
grazing on aquatic and semiaquatic vegetation, which reduces the cover 
needed by frogs and gartersnakes as well as the food supply for prey 
species such as tadpoles (Fernandez and Rosen 1996, pp. 10-12). 
Fernandez and Rosen (1996, pp. 10-12) also found that crayfish 
frequently burrow into stream banks, which leads to increased bank 
erosion, stream turbidity, and siltation of substrates. Creed (1994, p. 
2098) found that filamentous alga (Cladophora glomerata) was at least 
10-fold greater in aquatic habitat absent crayfish. Filamentous alga is 
an important component of aquatic vegetation that provides cover for 
foraging gartersnakes as well as microhabitat for prey species.
    Inman et al. (1998, p. 3) documented nonnative crayfish as widely 
distributed and locally abundant in a broad array of natural and 
artificial free-flowing and still-water habitats throughout Arizona, 
many of which overlapped the historical and current distribution of the 
northern Mexican gartersnake. Hyatt (undated, p. 71) concluded that the 
majority of waters in Arizona contained at least one species of 
crayfish. In surveying for northern Mexican and narrow-headed 
gartersnakes, Holycross et al. (2006, p. 14) found crayfish in 64 
percent of the sample sites in the Agua Fria watershed; in 85 percent 
of the sites in the Verde River watershed; in 46 percent of the sites 
in the Salt River watershed; and in 67 percent of the sites in the Gila 
River watershed. In total, crayfish were observed at 35 (61 percent) of 
the 57 sites surveyed across the Mogollon Rim (Holycross et al. 2006, 
p. 14), most of which were sites historically occupied by northern 
Mexican gartersnakes, or sites the investigators believed possessed 
suitable habitat and may be occupied based upon the known historical 
distribution of the subspecies.
    Several other authors have specifically documented the presence of 
crayfish in many areas and drainages throughout Arizona, which is 
testament to their ubiquitous distribution in Arizona and their strong 
colonizing abilities. These areas all fall within the range of the 
northern Mexican gartersnake and include the Kaibab National Forest 
(Sredl et al. 1995a, p. 7); the Coconino National Forest (Sredl et al. 
1995c, p. 7); the Watson Woods Riparian Preserve near Prescott (Nowak 
and Spille 2001, p. 33); the Tonto National Forest (Sredl et al. 1995b, 
p. 9); the Lower Colorado River (Ohmart et al. 1988, p. 150; Inman et 
al. 1998, Appendix B); the Huachuca Mountains (Sredl et al. 2000, p. 
10); the Arivaca Area (Rosen et al. 2001, Appendix I); Babocamari River 
drainage (Rosen et al. 2001, Appendix I); O'Donnell Creek drainage 
(Rosen et al. 2001, Appendix I); Santa Cruz River drainage (Rosen and 
Schwalbe 1988, Appendix I; Rosen et al. 2001, Appendix I); San Pedro 
River drainage (Inman et al. 1998, Appendix B; Rosen et al. 2001, 
Appendix I); Aqua Fria River drainage (Inman et al. 1998, Appendix B; 
Holycross et al. 2006, pp. 14, 15-18, 52-54); Verde River drainage 
(Inman et al. 1998, Appendix B; Holycross et al. 2006, pp. 14, 20-28, 
54-56); Salt River drainage (Inman et al. 1998, Appendix B; Holycross 
et al. 2006, pp. 15, 29-44, 56-60); Black River drainage (Inman et al. 
1998, Appendix B); San Francisco River drainage (Inman et al. 1998, 
Appendix B; Holycross et al. 2006, pp. 14, 49-50, 61); Nutrioso Creek 
drainage (Inman et al. 1998, Appendix B); Little Colorado River 
drainage (Inman et al. 1998, Appendix B); Leonard Canyon Drainage 
(Inman et al. 1998, Appendix B); East Clear Creek drainage (Inman et 
al. 1998, Appendix B); Chevelon Creek drainage (Inman et al. 1998, 
Appendix B); Eagle Creek drainage (Inman et al. 1998, Appendix B; 
Holycross et al. 2006, pp. 47-48, 60); Bill Williams drainage (Inman et 
al. 1998, Appendix B); Sabino Canyon drainage (Inman et al. 1998, 
Appendix B); Dry Creek drainage (Holycross et al. 2006, pp. 19, 53); 
Little Ash Creek drainage (Holycross et al. 2006, pp. 19, 54); Sycamore 
Creek drainage (Holycross et al. 2006, pp. 25, 54-55); East Verde River 
drainage (Holycross et al. 2006, pp. 21-22, 54); Oak Creek drainage 
(Holycross et al. 2006, pp. 23, 54); Pine Creek drainage (Holycross et 
al. 2006, pp. 24, 55); Spring Creek

[[Page 71813]]

drainage (Holycross et al. 2006, pp. 25, 55); Big Bonito Creek drainage 
(Holycross et al. 2006, pp. 29, 56); Cherry Creek drainage (Holycross 
et al. 2006, pp. 33, 57); East Fork Black River drainage (Holycross et 
al. 2006, pp. 34, 57); Haigler Creek drainage (Holycross et al. 2006, 
pp. 35, 58); Houston Creek drainage (Holycross et al. 2006, pp. 35-36, 
58); Rye Creek drainage (Holycross et al. 2006, pp. 37, 58); Tonto 
Creek drainage (Holycross et al. 2006, pp. 40-44, 59; Wallace et al. 
2008; pp. 243-244); Blue River drainage (Holycross et al. 2006, pp. 45, 
60); Campbell Blue River drainage (Holycross et al. 2006, pp. 46, 60); 
and the Gila River drainage (Inman et al. 1998, Appendix B; Holycross 
et al. 2006, pp. 45-50, 61). Like bullfrogs, crayfish can be very 
difficult, if not impossible, to eradicate once they have become 
established in an area (Rosen and Schwalbe 1996a, pp. 5-8; 2002a, p. 7; 
Hyatt undated, pp. 63-71).
    Nonnative Fish Distribution and Community Interactions. As 
indicated earlier in this document, nonnative fish are a threat to 
northern Mexican gartersnakes and their native anuran and fish prey. 
Similar to bullfrogs, predatory nonnative fish species, such as 
largemouth bass, also prey upon juvenile northern Mexican gartersnakes. 
Rosen et al. (2001, Appendix I) and Holycross et al. (2006, pp. 15-51) 
conducted large-scale surveys for northern Mexican gartersnakes in 
southeastern and central Arizona and narrow-headed gartersnakes in 
central and east-central Arizona and documented the presence of 
nonnative fish at many locations. Rosen et al. (2001, Appendix I) found 
nonnative fish in the following survey locations: The Arivaca Area; 
Babocamari River drainage; O'Donnell Creek drainage; Appleton-Whittell 
Research Ranch (Post Canyon) near Elgin; Santa Cruz River drainage; 
Agua Caliente Canyon; Santa Catalina Mountains; and the San Pedro River 
drainage. Holycross et al. (2006, pp. 14-15, 52-61) found nonnative 
fish in the Aqua Fria River drainage; the Verde River drainage; the Dry 
Creek drainage; the Little Ash Creek drainage; the Sycamore Creek 
drainage; the East Verde River drainage; the Oak Creek drainage; the 
Pine Creek drainage; the Big Bonito Creek drainage; the Black River 
drainage; the Canyon Creek drainage; the Cherry Creek drainage; the 
Christopher Creek drainage; the East Fork Black River drainage; the 
Haigler Creek drainage; the Houston Creek drainage; the Rye Creek 
drainage; the Salt River drainage; the Spring Creek drainage; the Tonto 
Creek drainage; the Blue River drainage; the Campbell Blue River 
drainage; the Eagle Creek drainage; and the San Francisco River 
drainage. Other authors have documented the presence of nonnative fish 
through their survey efforts in specific regions that include the Tonto 
National Forest (Sredl et al. 1995b, p. 8) and the Huachuca Mountains 
(Sredl et al. 2000, p. 10).
    Holycross et al. (2006, pp. 14-15) found nonnative fish species in 
64 percent of the sample sites in the Agua Fria watershed, 85 percent 
of the sample sites in the Verde River watershed, 75 percent of the 
sample sites in the Salt River watershed, and 56 percent of the sample 
sites in the Gila River watershed. In total, nonnative fish were 
observed at 41 of the 57 sites surveyed (72 percent) across the 
Mogollon Rim (Holycross et al. 2006, p. 14). Entirely native fish 
communities were detected in only 8 of 57 sites surveyed (14 percent) 
(Holycross et al. 2006, p. 14). While the locations and drainages 
identified above that are known to support populations of nonnative 
fish do not provide a thorough representation of the status of 
nonnative fish distribution Statewide in Arizona, it is well documented 
that nonnative fish have infiltrated the majority of aquatic 
communities in Arizona.
    Nonnative fish can also affect native amphibian populations. 
Matthews et al. (2002, p. 16) examined the relationship of gartersnake 
distributions, amphibian population declines, and nonnative fish 
introductions in high-elevation aquatic ecosystems in California. 
Matthews et al. (2002, p. 16) specifically examined the effect of 
nonnative trout introductions on populations of amphibians and mountain 
gartersnakes (Thamnophis elegans elegans). Their results indicated the 
probability of observing gartersnakes was 30 times greater in lakes 
containing amphibians than in lakes where amphibians have been 
extirpated by nonnative fish. These results supported prediction by 
Jennings et al. (1992, p. 503) that native amphibian declines will lead 
directly to gartersnake declines. Matthews et al. (2002, p. 20) noted 
that in addition to nonnative fish species adversely impacting 
amphibian populations that are part of the gartersnake's prey base, 
direct predation on gartersnakes by nonnative fish also occurs. 
Inversely, gartersnake predation on nonnative species, such as 
centrarchids, may physically harm the snake. Choking injuries to 
northern Mexican gartersnakes may occur from attempting to ingest 
nonnative spiny-rayed fish species (such as green sunfish and bass) 
because the spines located in the dorsal fins of these species can 
become lodged in, or cut into the gut tissue, of the snake, as observed 
in narrow-headed gartersnakes (Nowak and Santana-Bendix 2002, p. 25).
    Nonnative fish invasions can indirectly affect the health, 
maintenance, and reproduction of the northern Mexican gartersnake by 
altering its foraging strategy and foraging success. The more energy 
expended in foraging, coupled by the reduced number of small to medium-
sized prey fish available in lower densities, may lead to deficiencies 
in nutrition affecting growth and reproduction because energy is 
instead allocated to maintenance and the increased energy costs of 
intense foraging activity (Rosen et al. 2001, p. 19). In contrast, a 
northern Mexican gartersnake diet that includes both fish and 
amphibians such as leopard frogs provides larger prey items which 
reduce the necessity to forage at a higher frequency allowing metabolic 
energy gained from larger prey items to be allocated instead to growth 
and reproductive development. Myer and Kowell (1973, p. 225) 
experimented with food deprivation in common gartersnakes and found 
significant reductions in lengths and weights in juvenile snakes that 
were deprived of regular feedings versus the control group that were 
fed regularly at natural frequencies. Reduced foraging success means 
that individuals will become vulnerable to effects from starvation, 
which may, therefore, increase mortality rates in the juvenile size 
class and consequently affect recruitment of northern Mexican 
gartersnakes where their prey base has been compromised by nonnative 
species.
    Nonnative Species in Mexico. As in the United States, the native 
fish prey base for northern Mexican gartersnakes in Mexico has been 
dramatically affected by the introduction of nonnative species (Conant 
1974, pp. 471, 487-489; Miller et al. 2005, pp. 60-61; Abarca 2006). In 
the lower elevations of Mexico where northern Mexican gartersnakes 
occurred historically or are still found, there are approximately 200 
species of native freshwater fish documented with 120 native species 
under some form of threat and an additional 15 that have become extinct 
due to human activities, which include the introduction of nonnative 
species (Contreras Balderas and Lozano 1994, pp. 383-384). In 1979, The 
American Fisheries Society listed 69 species of native fish in Mexico 
as threatened or in danger of becoming extinct. Ten years later that 
number rose to 123 species, an increase of 78 percent

[[Page 71814]]

(Contreras Balderas and Lozano 1994, pp. 383-384). Miller et al. (2005, 
p. 60) concludes that some 20 percent of Mexico's native fish are 
threatened or in danger of becoming extinct. Nonnative species are 
increasing everywhere throughout Mexico, and this trend will have 
adverse impacts on native fish, according to Miller et al. (2005, p. 
61). A number of freshwater fish populations have been adversely 
affected by nonnative species in many locations, several of which were 
previously noted in the discussion under Factor A.
    At the time of our 2006 12-month finding, we had less information 
on the status and distribution of bullfrogs within Mexico. However, 
since that time, Luja and Rodr[iacute]guez-Estrella (2008, pp 17-22) 
examined the invasion of the bullfrog in Mexico. The earliest records 
of bullfrogs in Mexico were Nuevo Leon (1853), Tamaulipas (1898), 
Morelos (1968), and Sinaloa (1969) (Luja and Rodr[iacute]guez-Estrella 
2008, p 20). By 1976, the bullfrog was documented in 7 more States: 
Aguacalientes, Baja California Sur, Chihuahua, Distrito Federal, 
Puebla, San Luis Potosi, and Sonora (Luja and Rodr[iacute]guez-Estrella 
2008, p. 20). To date, Luja and Rodr[iacute]guez-Estrella (2008, p. 20) 
have recorded bullfrogs in 20 of the 31 Mexican States (65 percent of 
the states in Mexico) and suspect that they have invaded other States, 
but were unable to find documentation.
    Sponsored by the then Mexican Secretary of Aquaculture Support, 
bullfrogs have been commercially produced for food in Mexico in 
Yucatan, Nayarit, Morelos, Estado de Mexico, Michoac[aacute]n, 
Guadalajara, San Luis Potosi, Tamaulipas, and Sonora (Luja and 
Rodr[iacute]guez-Estrella 2008, p. 20). However, frog legs ultimately 
never gained popularity in Mexican culinary culture (Conant 1974, pp. 
487-489) and Luja and Rodr[iacute]guez-Estrella (2008, p. 22) point out 
that only 10 percent of these farms remain in production. Luja and 
Rodr[iacute]guez-Estrella (2008, p. 20 and 22) document instances where 
bullfrogs have escaped production farms and suspect the majority of the 
frogs that were produced commercially in farms that have since ceased 
operation have assimilated into surrounding habitat.
    Luja and Rodr[iacute]guez-Estrella (2008, p. 20) also state that 
Mexican people deliberately introduce bullfrogs for ornamental 
purposes, or ``for the simple pleasure of having them in ponds.'' The 
act of deliberately releasing bullfrogs into the wild in Mexico was 
cited by Luja and Rodr[iacute]guez-Estrella (2008, p. 21) as being 
``more common than we can imagine.'' To further compound these 
introductions, bullfrogs are available for purchase at Mexican pet 
stores (Luja and Rodr[iacute]guez-Estrella 2008, p. 22).
    Adverse effects such as predation upon, and competition with, 
northern Mexican gartersnakes and their prey base from bullfrog 
invasions in Mexico have been specifically documented with respect to 
Chiricahua leopard frogs, a primary prey item for northern Mexican 
gartersnakes (Luja and Rodr[iacute]guez-Estrella 2008, p. 21). Luja and 
Rodr[iacute]guez-Estrella (2008, p. 21) also stated that bullfrog 
eradication efforts in Mexico are often thwarted by their being favored 
by local communities. Currently, no regulation exists in Mexico to 
address the threat of bullfrog invasions (Luja and Rodr[iacute]guez-
Estrella 2008, p. 22).
    Rosen and Melendez (2006, p. 54) report bullfrog invasions to be 
prevalent in northwestern Chihuahua and northwestern Sonora, where the 
northern Mexican gartersnake is thought to occur. In many areas, native 
leopard frogs were completely displaced where bullfrogs were observed. 
Rosen and Melendez (2006, p. 54) also demonstrated the relationship 
between fish and amphibian communities in Sonora and western Chihuahua. 
Native leopard frogs, a primary prey item for the northern Mexican 
gartersnake, only occurred in the absence of nonnative fish and were 
absent from waters containing nonnative species, which included several 
major waters. In Sonora, Rorabaugh (2008, p. 25) also considers the 
bullfrog to be a significant threat to the northern Mexican gartersnake 
and its prey base.
    Unmack and Fagan (2004, p. 233) compared historical museum 
collections of nonnative fish species from the Gila River basin in 
Arizona and the Yaqui River basin in Sonora, Mexico, to gain insight 
into the trends in distribution, diversity, and abundance of nonnative 
fishes in each basin over time. They found that nonnative species are 
slowly but steadily increasing in all three parameters in the Yaqui 
Basin (Unmack and Fagan 2004, p. 233). Unmack and Fagan (2004, p. 233) 
predicted that, in the absence of aggressive management intervention, 
significant extirpations or range reductions of native fish species are 
expected to occur in the Yaqui Basin of Sonora, Mexico, which may have 
current populations of northern Mexican gartersnake, as did much of the 
Gila Basin before the introduction of nonnative species. Loss of native 
fishes will impact prey availability for the northern Mexican 
gartersnake and threaten its persistence in these areas.
    Summary of Factor C. While disease is not currently considered a 
direct threat to northern Mexican gartersnakes, Bd does have a 
widespread effect on anuran prey availability for the species. In 
addition, stress placed on northern Mexican gartersnakes as a result of 
threats discussed under Factor A may affect the health condition of 
individuals within populations affected by these threats, which may 
increase the potential for disease within current populations in the 
future.
    Direct predation by nonnative bullfrogs, crayfish, and fishes on 
northern Mexican garter snakes is a significant threat rangewide, as is 
predation on gartersnake prey species (competition) by these same 
groups of nonnative taxa. Nonnative fish, crayfish, and bullfrogs have 
reduced native populations of prey species throughout the range.

D. The Inadequacy of Existing Regulatory Mechanisms

    Currently, the northern Mexican gartersnake is considered ``State 
Endangered'' in New Mexico. In the State of New Mexico, an ``Endangered 
Species'' is defined as ``any species of fish or wildlife whose 
prospects of survival or recruitment within the State are in jeopardy 
due to any of the following factors: (1) The present or threatened 
destruction, modification, or curtailment of its habitat; (2) 
overutilization for scientific, commercial or sporting purposes; (3) 
the effect of disease or predation; (4) other natural or man-made 
factors affecting its prospects of survival or recruitment within the 
state; or (5) any combination of the foregoing factors'' as per New 
Mexico Statutory Authority (NMSA) 17-2-38.D. ``Take,'' defined as 
``means to harass, hunt, capture or kill any wildlife or attempt to do 
so'' by NMSA 17-2-38.L., is prohibited without a scientific collecting 
permit issued by the New Mexico Department of Game and Fish as per NMSA 
17-2-41.C and New Mexico Administrative Code (NMAC) 19.33.6. However, 
while the New Mexico Department of Game and Fish can issue monetary 
penalties for illegal take of northern Mexican gartersnakes, the same 
provisions are not in place for actions that result in loss or 
modification of habitat (NMSA 17-2-41.C and NMAC 19.33.6) (Painter 
2005).
    The northern Mexican gartersnake is considered a ``Candidate 
Species'' in the Arizona Game and Fish Department draft document, 
Wildlife of Special Concern (WSCA) (AGFD In Prep., p. 12). A 
``Candidate Species'' is one ``whose threats are known or suspected but 
for which substantial population declines from historical levels have 
not been documented (though they appear to

[[Page 71815]]

have occurred)'' (AGFD In Prep., p. 12). The purpose of the WSCA list 
is to provide guidance in habitat management implemented by land-
management agencies. Additionally, the northern Mexican gartersnake is 
considered a ``Tier 1b Species of Greatest Conservation Need'' in the 
Arizona Game and Fish Department draft document, Arizona's 
Comprehensive Wildlife Conservation Strategy (CWCS) (AGFD 2006a, p. 32; 
2006b). The purpose for the CWCS is to ``provide an essential 
foundation for the future of wildlife conservation and a stimulus to 
engage the States, federal agencies, and other conservation partners to 
strategically think about their individual and coordinated roles in 
prioritizing conservation efforts'' (AGFD 2006a, p. 2). A ``Tier 1b 
Species of Greatest Conservation Need'' is one that requires immediate 
conservation actions aimed at improving conditions through intervention 
at the population or habitat level (AGFD 2006a, p. 32).
    Prior to 2005, the Arizona Game and Fish Department allowed for 
take of up to four northern Mexican gartersnakes per person per year as 
specified in Commission Order Number 43. The Arizona Game and Fish 
Department defines ``take'' as ``pursuing, shooting, hunting, fishing, 
trapping, killing, capturing, snaring, or netting wildlife or the 
placing or using any net or other device or trap in a manner that may 
result in the capturing or killing of wildlife.'' The Arizona Game and 
Fish Department subsequently amended Commission Order Number 43, 
effective January 2005. Take of northern Mexican gartersnakes is no 
longer permitted in Arizona without issuance of a scientific collecting 
permit (Ariz. Admin. Code R12-4-401 et seq.). While the Arizona Game 
and Fish Department can seek criminal or civil penalties for illegal 
take of northern Mexican gartersnakes, the same provisions are not in 
place for actions that result in destruction or modification of 
northern Mexican gartersnake habitat.
    In addition to making the necessary regulatory changes to promote 
the conservation of the northern Mexican gartersnake, the Arizona Game 
and Fish Department continues as a strong partner in research and 
survey efforts that further our understanding of current populations 
within Arizona. They continue to assist with future conservation 
efforts and the establishment of long-term conservation partnerships.
    Gartersnakes are active, diurnal (daytime) foragers and humans 
encounter gartersnake species in riparian areas used for recreational 
purposes or for other reasons. These encounters can result in the 
capture, injury, or death of the gartersnake due to the lay person's 
fear or dislike of snakes (Rosen and Schwalbe 1988, p. 43; Ernst and 
Zug 1996, p. 75; Green 1997, pp. 285-286; Nowak and Santana-Bendix 
2002, p. 39). It is very difficult for the Arizona Game and Fish 
Department or the New Mexico Department of Fish and Game to monitor or 
even be aware of such forms of take. We believe that unregulated take 
occurs, particularly in areas frequently visited by the public with 
current populations of northern Mexican gartersnakes, such as at Page 
Springs and Bubbling Ponds hatcheries and along Tonto Creek near the 
town of Gisela. We are reasonably certain that the level of illegal 
field collecting by the hobbyist community is low because gartersnakes 
are relatively undesirable in amateur herpetological collections.
    Neither the New Mexico Department of Game and Fish, nor the Arizona 
Game and Fish Department have specified or mandated recovery goals for 
the northern Mexican gartersnake, nor has either State developed a 
conservation agreement or plan for this species.
    Throughout Mexico, the Mexican gartersnake is listed at the species 
level of its taxonomy as ``Amenazadas,'' or Threatened, by the 
Secretaria de Medio Ambiente y Recursos Naturales (SEMARNAT) (SEDESOL 
2001). Threatened species are ``those species, or populations of the 
same, likely to be in danger of disappearing in a short or medium 
timeframe, if the factors that negatively impact their viability, cause 
the deterioration or modification of their habitat or directly diminish 
the size of their populations continue to operate'' (SEDESOL 2001 (NOM-
059-ECOL-2001), p. 4). This designation prohibits taking of the 
species, unless specifically permitted, as well as prohibits any 
activity that intentionally destroys or adversely modifies its habitat 
(SEDESOL 2000 (LGVS) and 2001 (NOM-059-ECOL-2001)). Additionally, in 
1988, the Mexican Government passed a regulation that is similar to the 
National Environmental Policy Act of the United States (42 U.S.C. 4321 
et seq.). This Mexican regulation requires an environmental assessment 
of private or government actions that may affect wildlife or their 
habitat (SEDESOL 1988 (LGEEPA)).
    The Mexican Federal agency known as the Instituto Nacional de 
Ecolog[iacute]a (INE) is responsible for the analysis of the status and 
threats that pertain to species that are proposed for listing in the 
Norma Oficial Mexicana NOM-059 (the Mexican equivalent to a threatened 
and endangered species list), and if appropriate, the nomination of 
species to the list. INE is generally considered the Mexican 
counterpart to the United States' Fish and Wildlife Service. INE 
developed the Method of Evaluation of the Risk of Extinction of the 
Wild Species in Mexico (MER), which unifies the criteria of decisions 
on the categories of risk and permits the use of specific information 
fundamental to listing decisions. The MER is based on four independent, 
quantitative criteria: (1) Size of the distribution of the taxon in 
Mexico; (2) state (quality) of the habitat with respect to natural 
development of the taxon; (3) intrinsic biological vulnerability of the 
taxon; and (4) impacts of human activity on the taxon. INE began to use 
the MER in 2006; therefore, all species previously listed in the NOM-
059 were based solely on expert review and opinion in many cases. 
Specifically, until 2006, the listing process under INE consisted of a 
panel of scientific experts who convened as necessary for the purpose 
of defining and assessing the status and threats that affect Mexico's 
native species that are considered to be at risk and applying those 
factors to the definitions of the various listing categories. In 1994, 
when the Mexican gartersnake was placed on the NOM-059 (SEDESOL 1994 
(NOM-059-ECOL-1994), p. 46) as a threatened species, the decision was 
made by a panel of scientific experts.
    Although the Mexican gartersnake is considered a federally 
threatened species in Mexico, no recovery plan or other conservation 
planning occurs because of this status. Enforcement of the regulation 
protecting the gartersnake is sporadic, based on available resources 
and location. Based upon the information on the status of the species 
and the historic and continuing threats to its habitat in Mexico, our 
analysis concludes that protections afforded to the northern Mexican 
gartersnake may not be adequate to preclude the continued decline of 
this species throughout its range.
    Ortega-Huerta and Kral (2007, p. 1) found that land legislation 
within Mexico has changed considerably over recent years to integrate 
free market policies into local agricultural production methods. This 
may result in the loss of land management practices that protect the 
natural environment. In 1992, the Mexican Government made a 
constitutional amendment ending the Ejido's special legal status and 
permitting the sale of collectively controlled lands (Ortega-Huerta and 
Kral 2007, p. 2). An Ejido is an

[[Page 71816]]

amalgamation of various types of ownership of a particular piece of 
land, e.g., state, cooperative, communal, and private. Ejidos are 
generally managed in traditional means, which generally have less of an 
impact to the environment compared to more modern free market uses, 
resulting in higher levels of biodiversity (Ortega-Huerta and Kral 
2007, p. 2; Randall 1996, pp. 218-220; Kiernan 2000, pp. 13-23). The 
loss of regulation that prevented the division and sale of collectively 
controlled lands in Mexico is likely to reduce the protection of intact 
northern Mexican gartersnake habitat.
    Existing water laws in Arizona, New Mexico, and Mexico are 
inadequate to protect wildlife. The presence of water is a primary 
habitat constituent for the northern Mexican gartersnake. Gelt (2008, 
pp. 1-12) highlighted the fact that, because the existing water laws 
are so old, they reflect a legislative interpretation of the resource 
that is not consistent with what we know today; yet the laws have never 
been updated or amended to account for this discrepancy. For example, 
over 100 years ago when Arizona's water laws were written, the 
important connection between groundwater and surface water was not 
known (Gelt 2008, pp. 1-12). Gelt (2008, pp. 8-9) suggested that 
preserving stream flows and riparian areas may be better accomplished 
by curtailing surface water uses rather than ground water uses, and 
that the prior appropriation doctrine (appropriation of water rights 
based upon the water law concept of ``first in use, first in rights'') 
may be outdated and impractical for arid areas like Arizona.
    The majority of current populations of northern Mexican gartersnake 
in the United States occur on lands managed by the U.S. Bureau of Land 
Management and U.S. Forest Service. Although both agencies have 
riparian protection goals, neither agency has specific management plans 
for the northern Mexican gartersnake. The U.S. Bureau of Land 
Management considers the northern Mexican gartersnake as a ``Special 
Status Species,'' and agency biologists actively attempt to identify 
gartersnakes observed incidentally during fieldwork for their records 
(Young 2005). Otherwise, no specific protection or land-management 
consideration is afforded to the species on Bureau of Land Management 
lands.
    The U.S. Forest Service does not include northern Mexican 
gartersnake on their Management Indicator Species List, but it is 
included on the Regional Forester's Sensitive Species List. This means 
that northern Mexican gartersnakes are considered in land management 
decisions. Individual U.S. Forest Service biologists who work within 
the range of the northern Mexican gartersnake may opportunistically 
gather data for their records on gartersnakes observed incidentally in 
the field, although it is not required.
    Activities that could adversely affect northern Mexican 
gartersnakes and their habitat continue to occur throughout their 
current distribution on National Forest lands. Clary and Webster (1989, 
p. 1) stated that ``* * * most riparian grazing results suggest that 
the specific grazing system used is not of dominant importance, but 
good management is--with control of use in the riparian area a key 
item.'' Due to ongoing constraints in funding, staff levels, and time 
and regulatory compliance pertaining to monitoring and reporting duties 
tied to land management, proactive measures continue to be limited. 
These factors affect a land manager's ability to employ adaptive 
management procedures when effects to sensitive species or their 
habitat could be occurring at levels greater than anticipated in 
regulatory compliance mechanisms, such as in section 7 consultation 
under the Act for listed species that may co-occur with the northern 
Mexican gartersnake in an area. In other words, and due to the existing 
regulatory framework, some land managers may not have the flexibility 
required to adopt adaptive management where necessary to adequately 
account for adverse effects of projects on public lands.
    Riparian communities are complex and recognized as unique in the 
southwestern United States but are highly sensitive to many human-
caused land uses, as evidenced by the comparatively high number of 
federally listed riparian or aquatic species. Four primary prey species 
for the northern Mexican gartersnake, the Chiricahua leopard frog, Gila 
topminnow, Gila chub, and roundtail chub, are federally listed or were 
petitioned for listing. Other listed or proposed riparian species or 
their proposed or designated critical habitat overlap the current or 
historical distribution of the northern Mexican gartersnake. Despite 
secondary protections that may be afforded to the northern Mexican 
gartersnake from federally listed species or their critical habitat, 
riparian and aquatic communities continue to be adversely impacted for 
reasons previously discussed, contributing to the declining status of 
the northern Mexican gartersnake throughout its range in the United 
States.
    Summary of Factor D. Existing regulations within the range of the 
northern Mexican gartersnake address the direct take of individuals 
without a permit, and unpermitted take by recreationists or collectors 
is not thought to be at levels that impact the subspecies. Arizona and 
New Mexico statutes do not provide protection of habitat and 
ecosystems. Legislation in Mexico prohibits intentional destruction or 
modification of the snake's habitat, but neither that or prohibitions 
on take appear to be adequate to preclude the continued decline of the 
subspecies. Currently, there are no regulatory mechanisms in place that 
specifically target the conservation of northern Mexican gartersnake 
habitat. Legislation in Mexico has removed regulation of ejidos that 
promoted intact protection of important riparian and aquatic habitats. 
Regulations protecting the quantity and quality of water in riparian 
and aquatic communities are inadequate to protect water resources for 
the northern Mexican gartersnake, particularly in the face of the 
significant population growth expected within the historical range of 
the snake discussed under Factor A.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

    Competition With Other Species Within the Same Genus. Marcy's 
checkered gartersnake (Thamnophis marcianus marcianus) may impact the 
future conservation of the northern Mexican gartersnake in southern 
Arizona, although supporting data are limited. Marcy's checkered 
gartersnake is a semi-terrestrial species that is able to co-exist to 
some degree with riparian and aquatic nonnative predators. This is 
largely due to its ability to forage in more terrestrial habitats, 
specifically in the juvenile size classes (Rosen and Schwalbe 1988, p. 
31; Rosen et al. 2001, pp. 9-10). In every age class, the northern 
Mexican gartersnake forages in aquatic habitats where bullfrogs, 
nonnative sportfish, and crayfish also occur, which increases not only 
the encounter rate between the species but also the juvenile mortality 
rate of the northern Mexican gartersnake. As northern Mexican 
gartersnake numbers decline within a population, space becomes 
available for occupation by checkered gartersnakes. Marcy's checkered 
gartersnake subsequently affects the maximum number of northern Mexican 
gartersnakes that an area can maintain based upon available resources 
and could potentially accelerate the decline of or preclude reoccupancy 
by the northern Mexican gartersnake (Rosen and Schwalbe 1988, p. 31).
    Rosen et al. (2001, pp. 9-10) documented the occurrence of Marcy's

[[Page 71817]]

checkered gartersnakes out-competing and replacing northern Mexican 
gartersnakes at the San Bernardino National Refuge and surrounding 
habitats of the Black Draw. They suspected that the drought from the 
late 1980s through the late 1990s played a role in the degree of 
competition for aquatic resources, provided an advantage to the more 
versatile Marcy's checkered gartersnake, and expedited the decline of 
the northern Mexican gartersnake. The competition between these two 
species, in combination with other factors described above that have 
adversely affected the northern Mexican gartersnake prey base and the 
suitability of occupied and formerly occupied habitat, may be 
contributing to the decline of this species.
    Current and Future Effects from Changes in Climatic Patterns and 
Drought. Seagar et al. (2007, pp. 1181-1184) analyzed 19 different 
computer models of differing variables to estimate the future 
climatology of the southwestern United States and northern Mexico in 
response to predictions of changing climatic patterns. All but 1 of the 
19 models predicted a drying trend within the Southwest; one predicted 
a trend toward a wetter climate (Seager et al. 2007, p. 1181). A total 
of 49 projections were created using the 19 models and all but 3 
predicted a shift to increasing aridity (dryness) in the Southwest as 
early as 2021-2040 (Seager, et al. 2007, p. 1181). The northern Mexican 
gartersnake and its prey base depend on permanent or nearly permanent 
water for survival. A large percentage of habitat within the current 
distribution of the northern Mexican gartersnake is predicted to be at 
risk of becoming more arid (Seager et al. 2007, pp. 1183-1184), which 
has severe implications to the integrity of aquatic and riparian 
ecosystems and the water that supports them. Potential drought 
associated with changing climatic patterns may not only adversely 
affect habitat of the northern Mexican gartersnake, but also its prey. 
Amphibians may be among the first vertebrates to exhibit broad-scale 
changes in response to changes in global climatic patters due to their 
sensitivity to changes in moisture and temperature (Reaser and 
Blaustein 2005, p. 61). Changes in temperature and moisture, combined 
with the ongoing threat to amphibians from the persistence of Bd may 
cause prey species to experience increased physiological stress and 
decreased immune system function, possibly leading to disease outbreaks 
(Carey and Alexander 2003, pp. 111-121; Pounds et al. 2006, pp. 161-
167).
    Changes to climatic patterns are predicted to have implications for 
the effect of, and management for, nonnative species within the 
distribution of the northern Mexican gartersnake. Based upon climate 
change models, nonnative species biology, and ecological observations, 
Rahel et al. (2008, p. 551) conclude that climate change could foster 
the expansion of nonnative aquatic species into new areas, magnify the 
effects of existing aquatic nonnative species where they currently 
occur, increase nonnative predation rates, and heighten the virulence 
of disease outbreaks in North America. Many of the nonnative species 
have similar, basic ecological requirements as our native species, such 
as the need for permanent or nearly permanent water. Therefore, it is 
likely that effects from changes to climatic patterns (such as a trend 
towards a more arid environment) that negatively affect nonnative 
species such as bullfrogs and nonnative fish may also negatively affect 
native prey species for the northern Mexican gartersnake.
    Changes to climatic patterns may warm water temperatures, alter 
stream flow events, and may increase demand for water storage and 
conveyance systems (Rahel and Olden 2008, pp. 521-522). Warmer water 
temperatures across temperate regions are predicted to expand the 
distribution of existing aquatic nonnative species by providing 31 
percent more suitable habitat for aquatic nonnative species, which are 
often tropical in origin and adaptable to warmer water temperatures. 
This conclusion is based upon studies that compared the thermal 
tolerances of 57 fish species with predictions made from climate change 
temperature models (Mohseni et al. 2003, p. 389). Eaton and Scheller 
(1996, p. 1,111) reported that while several cold-water fish species in 
North America are expected to have reductions in their distribution 
from effects of climate change, several warmwater fish species are 
expected to increase their distribution. In the southwestern United 
States, this situation may occur where the quantity of water is 
sufficient to sustain effects of potential prolonged drought conditions 
but where water temperature may warm to a level found suitable to 
harmful nonnative species that were previously physiologically 
precluded from occupation of these areas. Species that are particularly 
harmful to northern Mexican gartersnake populations such as the green 
sunfish, channel catfish, largemouth bass, and bluegill are expected to 
increase their distribution by 7.4 percent, 25.2 percent, 30.4 percent, 
and 33.3 percent, respectively (Eaton and Scheller 1996, p. 1,111).
    Rahel and Olden (2008, p. 526) expect that increases in water 
temperatures in drier climates such as the southwestern United States 
will result in periods of prolonged low flows and stream drying. These 
effects from changing climatic conditions may have profound effects on 
the amount, permanency, and quality of habitat for the northern Mexican 
gartersnake and its prey base. Warmwater nonnative species such as red 
shiner, common carp, mosquitofish, and largemouth bass are expected to 
benefit from prolonged periods of low flow (Rahel and Olden 2008, p. 
527).
    Data specific to changing climatic patterns in Mexico, other than 
the Seager et al. (2007) climate change modeling, are limited. However, 
because the predictive climate models include northern Mexico, we 
assume that the changes predicted for the southwestern United States 
will likely be similar.
    The effects of the water withdrawals discussed above may be 
exacerbated by the current, long-term drought facing the arid 
southwestern United States. Philips and Thomas (2005, pp. 1-4) provided 
streamflow records that indicate that the drought Arizona experienced 
between 1999 and 2004 was the worst drought since the early 1940s and 
possibly earlier. The Arizona Drought Preparedness Plan Monitoring 
Technical Committee (ADPPMTC) (2008) assessed Arizona's drought status 
through June 2008 in watersheds where the northern Mexican gartersnake 
occurs or historically occurred. They found that the Verde, Agua Fria, 
San Pedro, Santa Cruz, and Whitewater Draw watersheds continue to 
experience moderate drought (ADPPMTC 2008). Whereas the Salt, Upper 
Gila, Lower Gila, and Lower Colorado watersheds were abnormally dry 
(ADPPMTC 2008). Ongoing drought conditions have depleted recharge of 
aquifers and decreased baseflows in the region. While drought periods 
have been relatively numerous in the arid Southwest from the mid-1800s 
to the present, the effects of human-caused impacts on riparian and 
aquatic communities have compromised the ability of these communities 
to function under the additional stress of prolonged drought 
conditions. Holycross et al. (2006, pp. 52-53) recently documented the 
effects of drought on northern Mexican gartersnake habitat in the 
vicinity of Arcosante along the Agua Fria River and at Big Bug Creek. 
The streams were completely dry and therefore unsuitable northern 
Mexican gartersnake habitats.

[[Page 71818]]

    Summary of Factor E. It is unlikely that competition with other 
gartersnakes will be a significant cause of decline in northern Mexican 
gartersnake populations in comparison to other threats we have 
discussed. All but one model evaluating changing climatic patterns for 
the southwestern United States and northern Mexico predict a drying 
trend for the region (Seagar et al. 2007, pp. 1181-1184). We 
acknowledge that drought and the loss of surface water in riparian and 
aquatic communities are related to changing climatic conditions (Seagar 
et al. 2007, pp. 1181-1184). The extent to which changing climate 
patterns will affect the northern Mexican gartersnake is not known with 
certainty at this time. However, threats to the northern Mexican 
gartersnake indentified in Factors A and C will likely be exacerbated 
by changes to climatic patterns in the southwestern United States due 
to resulting increasing drought and reduction of surface waters if the 
predicted patterns are realized. Data specific to changes in climatic 
patterns in Mexico are limited, but because the models for the 
southwestern United States included northern Mexico, we believe that 
the effect from the changing climatic patterns will exacerbate threats 
due to Factors A and C in that country as well.

Foreseeable Future

    When determining whether a species is in danger of extinction 
throughout all or a significant portion of its range, or is likely to 
become in danger of extinction in the foreseeable future, we must 
identify that foreseeable future for the species. The Act does not 
specifically define the term ``foreseeable future.'' In discussing the 
concept of foreseeable future for the northern Mexican gartersnake, we 
considered (1) the biological and demographic characteristics of the 
species (such as generation times, population genetics, trends in age-
class distribution within current populations, etc.); (2) our ability 
to predict or extrapolate the effects of threats facing the species 
into the future; and (3) the relative permanency or irreversibility of 
these threats. Of the threats to the northern Mexican gartersnake and 
its prey base that have been discussed above in our analysis of the 
threats, we believe the threat of nonnative species presents the most 
widespread, imminent, and serious threat to the long-term 
sustainability of this subspecies. Therefore, we concentrate primarily 
upon this threat to the northern Mexican gartersnake in our analysis of 
the subspecies' viability into the foreseeable future. Because our 
knowledge of the threats to and status of the northern Mexican 
gartersnake in Mexico is not as robust as that for the United States, 
our analysis focuses on the United States and presumes (1) similar 
human-caused threats occur to the subspecies' habitat in areas in 
proximity to human population centers in Mexico, and (2) a time-lagged 
effect, with respect to nonnative species invasions, within more remote 
habitat in Mexico as postulated in Unmack and Fagan (2004, pp. 233-
243).
    Based on museum records found in Holycross et al. (2006, Appendix 
F), we expect the northern Mexican gartersnake retained its entire 
historic distribution within the United States through the 1920s and 
likely into the 1930s. Activities such as the construction of dams and 
water diversions that occurred throughout the early to mid-1900s for 
agriculture and regional economic development likely eliminated surface 
flow throughout stream reaches with occupied habitat, which led to 
subsequent and widespread extirpations of northern Mexican gartersnake 
populations in areas such as the lower Gila and Salt rivers in Arizona.
    After the period of dam construction and the subsequent creation of 
reservoirs, widespread nonnative fish stocking efforts ensued 
throughout Arizona beginning during the mid 1900's. In the Verde River 
system alone, Rinne et al. (1998, p. 3) estimated that over 5,300 
independent stocking actions occurred that involved 12 different 
species of nonnative fish species since the 1930s and 1940s. If we 
extrapolate that effort over the same timeframe for other historically 
occupied, larger-order systems known as recreational fisheries such as 
the Salt, upper Gila, Colorado, Santa Cruz, Agua Fria, and San Pedro 
rivers, Tonto and Oak creeks, and other tributaries with significant 
flow throughout central and southern Arizona, in addition to the other 
private stockings of stock tanks and other isolated habitat, the 
magnitude of the nonnative species invasion over this timeframe becomes 
clear. Subsequent to these efforts, but to a lesser extent, the spread 
of bullfrogs and crayfish, both purposefully and incidentally, 
commenced during the 1970s and 1980s (Tellman 2002, p. 43). We estimate 
that near 100 percent of the habitat that historically supported 
northern Mexican gartersnakes has been invaded over-time, either 
purposefully or indirectly through dispersal, by nonnative species 
whether they be nonnative fish, bullfrogs, or crayfish. The effects 
from this influx of nonnative species throughout the American Southwest 
resulted in significant declines in native fish and ranid frog 
distribution and abundance, and the subsequent listing of 19 of 
Arizona's 31 native fish species throughout the last 35 years (see 
discussion under ``Declines in the Northern Mexican Gartersnake Native 
Fish Prey Base'' within Listing Factor C). The decline of native fish 
species that depend on native riparian and aquatic systems provides 
evidence of overall impacts to the affected biotic communities. These 
effects were discussed in detail in Factor A and Factor C above.
    In response to the impacts to the northern Mexican gartersnake and 
its native prey base discussed above and in our analysis of threats, 
the distribution of northern Mexican gartersnake has been reduced to 
approximately 10 percent of its historic range within the United States 
over the last 80 years. However, because of the sensitivity of the 
northern Mexican gartersnake to community-wide effects from nonnative 
species, we believe the most significant period of declines and 
subsequent extirpations of entire populations likely coincided with the 
proliferation of nonnative species beginning in the 1940s and 1950s, 
most notably with the widespread introduction and expansion of 
sportfish such as largemouth bass, green sunfish, and channel and 
flathead catfish. In addition, further declines and extirpations likely 
resulted from systematic bullfrog introductions, beginning in the 1970s 
and early 1980s, caused by the bullfrog's natural capacity to disperse 
and its predation behavior on the northern Mexican gartersnake and 
associated prey base. In several areas where northern Mexican 
gartersnakes remain in the United States, we have observed skewed age-
class distributions within populations that favor large-bodied, older 
individuals with significantly less newborns and juveniles (Holm and 
Lowe 1995, pp. 33-34; Holycross et al. 2006, pp. 41-44; Wallace et al. 
2008, pp. 243-244). These trends are particularly apparent in areas 
where habitat remains structurally intact, but where nonnative species 
maintain stable populations.
    The observed effects of nonnative species on age-class distribution 
and recruitment are an important influence on the maintenance of 
current populations to be considered in our evaluation of the 
foreseeable future for this species. We were not able to locate any 
quantitative studies on longevity of the northern Mexican gartersnake 
in the wild, or on gartersnakes in general. However, Bowler (1975) 
recorded longevity of amphibians and reptiles in captivity that 
included several species

[[Page 71819]]

within the genus Thamnophis. Lifespans of six different gartersnake 
species ranged from 2 to 10 years (Bowler 1975). These data are old, 
however, and innovations in the captive care of specimens in the 
subsequent three decades have improved our knowledge of captive 
husbandry for these species, allowing longer lifespans in captivity. 
Simply knowing that individuals of a certain species are capable of 
living a certain number of years under ideal captive conditions means 
that longevity in the wild might be longer than suspected, although 
usually shorter than in captivity. Ernst and Zug (1996, p. 39) provide 
one record on wild longevity in the common gartersnake (Thamnophis 
sirtalis) as nine years. It is reasonable to conclude that the northern 
Mexican gartersnake, a similarly sized snake of the same genus, may 
have similar longevity in the wild.
    The average age of sexual maturity is 2.5 years for female northern 
Mexican gartersnakes, and 2 years for males. Females may only breed 
once every 2 years (Rosen and Schwalbe 1988, pp. 16-17). Considering 
these timeframes, a female northern Mexican gartersnake might reproduce 
up to three times during a maximum lifespan in the wild. We are aware 
of no studies on the survivorship of northern Mexican gartersnakes in 
the wild. However, Jayne and Bennett (1990, pp. 1209-1221) studied 
survivorship within a population of common gartersnakes, a similar 
species, and found that, in two groups of similarly aged snakes within 
that population, survivorship during the first year following birth was 
29 percent and 43 percent in this 2-year study, although we are unaware 
of the presence, type, or extent of threats that may have influenced 
survivorship. Only 16 percent of one group survived into their second 
year, while 50 percent of the second group survived into their second 
year (Jayne and Bennett 1990, pp. 1209-1221). Jayne and Bennett (1990, 
pp. 1209-1221) calculated that 15 percent of individuals live to be 
older than 2 years. Adult survival rates in common gartersnakes appears 
to be quite variable, however. In Manitoba, adult year-to-year 
survivorship was calculated at 34 percent and at 67 percent in the 
Northwest Territories (Larsen and Gregory 1989, pp. 84-85; Larsen et 
al. 1993, pp. 338-342). Based on demographic studies on the common 
gartersnake and making a conservative estimate on survivorship and 
fecundity rates without consideration of the presence or degree of 
threats, it is reasonable to presume that, on average, two individual 
northern Mexican gartersnakes from each litter may reach reproductive 
age. Whether or not these individuals find a mate and successfully 
reproduce depends upon the population density and the degree of threats 
that may be acting on a given population.
    In Table 4 of Holycross et al. (2006, p. 64), capture rates of 
northern Mexican gartersnakes during surveys in 2004 and 2005 along the 
Mogollon Rim of Arizona were compared to those from a previous study, 
Rosen and Schwalbe (1988, Appendix I). In total, capture rates in nine 
different stream reaches surveyed by both sets of investigators were 
compared. Rosen and Schwalbe (1988, Appendix I) spent 128 person-search 
hours to capture a total of 10 individuals at six of the nine (66 
percent) stream reaches. Holycross et al. (2006, p. 64) spent 142 
person-search hours [11 percent more than Rosen and Schwalbe (1988, 
Appendix I)] and found six total individuals in only two stream reaches 
of the nine (22 percent) that were comparably surveyed. These data 
indicate that Holycross et al. (2006, p. 64) found northern Mexican 
gartersnakes at 66 percent fewer locations than did Rosen and Schwalbe 
(1988, Appendix I) which indicate potential population extirpations in 
two-thirds of populations during that 17-year time period. The averaged 
number of person-search hours per capture was 12.8 hours in 1988 (Rosen 
and Schwalbe 1988, Appendix I), but approximately twice that (23.6 
person-search hours) in 2004-2005 (Holycross et al. 2006, p. 64).
    Today, there remain three areas in the United States where the 
northern Mexican gartersnake is most reliably found, the Upper Santa 
Cruz River in the San Rafael Valley of south-central Arizona, Tonto 
Creek from the vicinity of Gisela downstream to Roosevelt Lake, and the 
Page Springs/Bubbling Ponds hatchery complex along Oak Creek slightly 
upstream of its confluence with the Verde River. These populations are 
geographically disjunct, genetically isolated from one-another, and 
lack significant, nearby source populations to serve as a natural 
source of individuals for recolonization should any one of them become 
extirpated. Therefore, these populations remain highly vulnerable to 
the effects of the threats discussed in detail in Factors A-E above, 
and to stochastic events not previously anticipated. If we extrapolate 
the last 20 years of population trends documented in the previous 
paragraph, we anticipate that in approximately 15-20 years, these 
remaining, currently reliable populations may become extirpated should 
current trends persist into the future. This is not to say that the 
northern Mexican gartersnake, in its entirety, will be extirpated from 
the United States during this time frame because it would remain 
plausible that extremely low-density populations of a few individuals 
may persist in other areas past this time frame.
    Considering the above discussion on (1) reproduction biology, 
observed trends in population demographics, and age-class survivorship; 
(2) the time periods that correlated to the onset of the most 
significant threats to the species and number of years it has taken for 
a 90 percent reduction of the distribution of the subspecies in the 
United States; (3) the relative isolation and disjunct nature of 
current populations and their inability to serve as a basis for genetic 
exchange; (4) comparative analysis between comprehensive survey results 
spread over 17 years over a significant portion of the subspecies' 
historical distribution in the United States and subsequent 
extrapolations for remaining populations; and (5) the future potential 
for threats most detrimental to the long-term viability of the 
subspecies in the United States (such as the continued proliferation of 
nonnative species), we anticipate that northern Mexican gartersnake may 
be predominantly extirpated from the U.S. within 25 years. We base this 
estimate largely upon our most current observations of population 
trends and their response to threats posed by nonnative species, as 
discussed above.
    We do not expect that current policies on native fish restoration 
and recovery will change. These policies now focus activities on 
replacing fisheries which contain nonnative species with wholly native 
fisheries in stream types that are generally not suitable for northern 
Mexican gartersnakes, rather than mainstem rivers of lower gradient 
which provide preferred habitat for the northern Mexican gartersnake. 
We have also discussed in Factor C above the widespread influence of 
crayfish and bullfrogs on riparian and aquatic communities and the 
significant difficulty of removing them from areas once they have 
become established. As discussed in Factor E, climate change and 
subsequent drought will likely exacerbate the threats to the northern 
Mexican gartersnake related to habitat and prey base. Thus, the 
foreseeable future for the northern Mexican gartersnake in the U.S. is 
25 years to 2033.
    With respect to the species' foreseeable future throughout its 
distribution in Mexico, threats to the northern Mexican gartersnake 
from human-related activities are most likely

[[Page 71820]]

in areas adjacent to human population centers, and these threats affect 
the subspecies to a similar degree as observed in the United States. We 
conclude that changes to climatic patterns will affect northern Mexican 
gartersnake habitat in similar ways in the more northern latitudes of 
Mexico as has been anticipated for the southwestern United States. 
Therefore, we estimate the foreseeable future in populated areas of 
Mexico within the range of the subspecies to be 25 years.
    Unmack and Fagan (2004, p. 233) hypothesized that a time-lagged 
effect is occurring in portions of Mexico with respect to nonnative 
species invasions, due primarily to the remoteness of some areas. 
However, there is widespread consensus that it is inevitable that 
nonnative species will continue to invade new habitats throughout 
Mexico, leading to further declines and extirpations of the northern 
Mexican gartersnake and its prey species in Mexico (Conant 1974, pp. 
471, 487-489; Contreras Balderas and Lozano 1994, pp. 383-384; Miller 
et al. 2005, pp. 60-61; Abarca 2006; Luja and Rodr[iacute]guez-Estrella 
2008, pp. 17-22). Consequently, for the more remote areas of Mexico, 
the foreseeable future may be beyond 2033, but we are not confident 
estimating how far beyond.

Significant Portion of the Range Analysis

    As required by the Act, we considered the five potential threat 
factors to assess whether the northern Mexican gartersnake is 
threatened or endangered throughout all or a significant portion of its 
range. When considering the listing status of the species, the first 
step in the analysis is to determine whether the species is in danger 
of extinction throughout all of its range. If this is the case, then we 
list the species in its entirety. For instance, if the threats to a 
species are directly acting on only a portion of its range, but they 
are at such a large scale that they place the entire species in danger 
of extinction, we would list the entire species.
    We next consider whether any significant portion of the northern 
Mexican gartersnake range meets the definition of endangered or is 
likely to become endangered in the foreseeable future (threatened). On 
March 16, 2007, a formal opinion was issued by the Solicitor of the 
Department of the Interior, ``The Meaning of `In Danger of Extinction 
Throughout All or a Significant Portion of Its Range' '' (USDOI 2007, 
pp. 1-36). A portion of a species' range is significant if it is part 
of the current range of the species and is important to the 
conservation of the species because it contributes meaningfully to the 
representation, resiliency, or redundancy of the species. The 
contribution must be at a level such that its loss would result in a 
decrease in the ability of the species to persist.
    The first step in determining whether a species is threatened or 
endangered in a significant portion of its range is to identify any 
portions of the range of the species that warrant further 
consideration. The range of a species can theoretically be divided into 
portions in an infinite number of ways. To identify portions that 
warrant further consideration, we determine whether there is 
substantial information indicating that (1) the portions may be 
significant, and (2) the species may be in danger of extinction there 
or likely to become so within the foreseeable future. In practice, a 
key part of this analysis is whether the threats are geographically 
concentrated in some way. If the threats to the species are essentially 
uniform throughout its range, no portion is likely to warrant further 
consideration. Moreover, if any concentration of threats applies only 
to portions of the range that are unimportant to the conservation of 
the species, such portions will not warrant further consideration.
    If we identify any portions that warrant further consideration, we 
then determine whether the species is threatened or endangered in any 
significant portion. If we determine that a portion of the range is not 
significant, we do not determine whether the species is threatened or 
endangered there.
    The terms ``resiliency,'' ``redundancy,'' and ``representation'' 
are intended to be indicators of the conservation value of portions of 
the range. Resiliency of a species allows it to recover from periodic 
disturbances. A species will likely be more resilient if large 
populations exist in high-quality habitat that is distributed 
throughout its range in a way that captures the environmental 
variability available. A portion of the range of a species may make a 
meaningful contribution to the resiliency of the species if the area is 
relatively large and contains particularly high-quality habitat, or if 
its location or characteristics make it less susceptible to certain 
threats than other portions of the range. When evaluating whether or 
how a portion of the range contributes to resiliency of the species, we 
evaluate the historical value of the portion and how frequently the 
portion is used by the species, if possible. The range portion may 
contribute to resiliency for other reasons; for instance, it may 
contain an important concentration of certain types of habitat that are 
necessary for the species to carry out its life-history functions, such 
as breeding, feeding, migration, dispersal, or wintering.
    Redundancy of populations may be needed to provide a margin of 
safety for the species to withstand catastrophic events. This concept 
does not mean that any portion that provides redundancy is per se a 
significant portion of the range of a species. The idea is to conserve 
enough areas of the range so that random perturbations in the system 
only act on a few populations. Therefore, we examine each area based on 
whether that area provides an increment of redundancy that is important 
to the conservation of the species.
    Adequate representation ensures that the species' adaptive 
capabilities are conserved. Specifically, we evaluate a range portion 
to see how it contributes to the genetic diversity of the species. The 
loss of genetically based diversity may substantially reduce the 
ability of the species to respond and adapt to future environmental 
changes. A peripheral population may contribute meaningfully to 
representation if there is evidence that it provides genetic diversity 
due to its location on the margin of the species' habitat requirements.
    Based upon factors that contribute to our analysis of whether a 
species or subspecies is ``In Danger of Extinction Throughout All or a 
Significant Portion of Its Range,'' and in consideration of the status 
of and threats to the northern Mexican gartersnake discussed 
previously, we find that significant threats to the continued existence 
of the northern Mexican gartersnake occur throughout all of its range 
in the United States and Mexico. Therefore, it is not necessary to 
conduct further analysis with respect to the significance of any 
portion of its range at this time.

Finding

    We have carefully examined the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by the northern Mexican gartersnake. We reviewed the petition, 
information available in our files, other published and unpublished 
information submitted to us during the public comment periods following 
our 90-day and previous 12-month petition findings and consulted with 
recognized northern Mexican gartersnake experts and other Federal, 
State, Tribal, and Mexican resource agencies. On the basis of the best 
scientific and commercial information available, we find that listing 
of the northern Mexican

[[Page 71821]]

gartersnake as threatened or endangered throughout its range in the 
United States and Mexico, based on its rangewide status, is warranted, 
due to the present or threatened destruction, modification or 
curtailment of its habitat; predation; and the inadequacy of existing 
regulatory mechanisms. However, as explained in more detail below, an 
immediate proposal of a regulation implementing this action is 
precluded by higher priority listing actions, and progress is being 
made to add or remove qualified species from the Lists of Endangered 
and Threatened Wildlife and Plants.
    We recognize there have been remarkable declines in the 
distribution and abundance of the northern Mexican gartersnake within 
its distribution in the United States, which are primarily attributed 
to individual and community interactions with nonnative species that 
occur in every single locality where northern Mexican gartersnakes have 
been documented. We identified the ecological mechanisms for which 
nonnative interactions occur to include: (1) Direct predation on 
northern Mexican gartersnakes by nonnative species; and (2) the effects 
of a diminished prey base via nonnative species preying upon and 
competing with native prey species as documented in a large body of 
scientific research, which is cited and analyzed in our discussion of 
threats under each of the listing factors.
    Throughout the range of the northern Mexican gartersnake, 
literature documents the cause and effect relationship of modification 
of the food chains within native riparian and aquatic communities. The 
substantial decline of primary native prey species, such as leopard 
frogs and native fish, has contributed significantly to the decline of 
a primary predator, the northern Mexican gartersnake. In this respect, 
the northern Mexican gartersnake is considered an indicator species, or 
a species that can be used to gauge the condition of a particular 
habitat, community, or ecosystem. The synergistic effect of nonnative 
species both reducing the prey base of, and directly preying upon, 
northern Mexican gartersnakes has placed significant pressure upon the 
viability and sustainability of current northern Mexican gartersnake 
populations and has led to significant fragmentation and risks to the 
continued viability of current populations. The evolutionary biology of 
the northern Mexican gartersnake, much like that of native fish and 
leopard frogs, has left the species without adaptation to and 
defenseless against the effect of nonnative species invasions.
    The decline of the northern Mexican gartersnake has been 
exacerbated by historical and ongoing threats to its habitat in the 
United States. The threats identified and discussed above in detail 
under Factor A include: (1) The modification and loss of ecologically 
valuable riparian and aquatic communities; (2) urban and rural 
development; (3) road construction, use, and maintenance; (4) human 
population growth; (5) groundwater pumping, surface water diversions, 
and flood; (6) improper livestock grazing; (7) catastrophic wildfire 
and wildfire in non-fire adapted communities; and (8) undocumented 
immigration and international border enforcement and management. In 
addition, disease and parasitism, climate change, and drought may pose 
threats to the northern Mexican gartersnake and its prey base.
    As a result of our assessment, we find that certain land use 
activities, such as road construction and use, improper livestock 
grazing, undocumented immigration and associated international border 
enforcement and management activities, and some types of development, 
pose a more significant risk to highly fragmented, low-density 
populations of northern Mexican gartersnakes, particularly in the 
presence of nonnative species. We know of no current population of 
northern Mexican gartersnakes in the United States that does not occur 
in the presence of nonnative species.
    In this finding, we have emphasized the importance of the 
protection of the ecosystems upon which the northern Mexican 
gartersnake depends, and documented the status of riparian and aquatic 
communities in the southwestern United States and much of Mexico. 
Evidence of the current precarious status of native riparian and 
aquatic ecosystems in the southwestern United States is the proportion 
of riparian or aquatic obligate species that are either federally 
listed under the Act or candidates for listing. In Arizona, there is a 
total of 73 species that meet these criteria. Of these 73 species, 38 
(52 percent) are riparian or aquatic. Of the 45 vertebrate species that 
are either federally listed or candidates for listing in Arizona, 30 
(67 percent) have riparian or aquatic life histories, and 19 (42 
percent) are potential northern Mexican gartersnake prey species in 
larval, juvenile, or adult forms, based on overlapping historical 
distributions. These data suggest that the riparian and aquatic 
ecosystems in Arizona, upon which the northern Mexican gartersnake 
depends, cannot currently support many of the species that rely upon 
them.
    In making this finding, we acknowledge that the Mexican Government 
has found the Mexican gartersnake to be in danger of disappearance in 
the short-or medium-term future in their country from the destruction 
and modification of its habitat or from the effects of shrinking 
population sizes, or both, and has, therefore, listed the species as 
Threatened, under the listing authority of SEMARNAT (SEDESOL 2001). We 
have provided an assessment of the status of the northern Mexican 
gartersnake and its habitat in Mexico, but we also rely on the 
assessment of the species made by the Mexican Government in listing the 
entity as Threatened. The available literature supports the assessment 
of the species made by the Mexican Government, which indicates that 
nonnative species and habitat modification and loss are adversely 
affecting the status of northern Mexican gartersnakes in Mexico.
    Additionally, land uses, such as urbanization and development, 
improper livestock grazing, water diversions and groundwater pumping, 
and impoundments, have resulted in losses of vegetative cover, 
deforestation, erosion, and pollution that have modified or destroyed 
historical northern Mexican gartersnake habitat in Mexico. 
Collectively, the impacts of traditional rural land management 
practices and growth of the economic sector, infrastructure, and 
population growth are expected to continue into the future.
    We have reviewed the available information to determine if the 
existing and foreseeable threats pose an emergency. We have determined 
that an emergency listing is not warranted for this subspecies at this 
time because, within the current distribution of the subspecies in 
Mexico, there are at least some populations of the northern Mexican 
gartersnake that exist in relatively natural conditions that are 
unlikely to change in the short-term. However, if at any time we 
determine that emergency listing of the northern Mexican gartersnake is 
warranted, we will initiate an emergency listing.
    The Service adopted guidelines on September 21, 1983 (48 FR 43098) 
to establish a rational system for allocating available appropriations 
to the highest priority species when adding species to the Lists of 
Endangered or Threatened Wildlife and Plants or reclassifying 
threatened species to endangered status. The system places greatest 
importance on the immediacy and magnitude of

[[Page 71822]]

threats, but also factors in the level of taxonomic distinctiveness by 
assigning priority in descending order to monotypic genera, full 
species, and subspecies (or equivalently, distinct population segments 
of vertebrates). As a result of our analysis of the best available 
scientific and commercial information, we have assigned the northern 
Mexican gartersnake a Listing Priority Number of 3, based on high 
magnitude and immediacy of threats. One or more of the threats 
discussed above is occurring in each known population in the United 
States and throughout historically occupied habitats in Mexico. These 
threats are ongoing and, in some cases (e.g., nonnative species), 
considered irreversible. While we conclude that listing the northern 
Mexican gartersnake is warranted, an immediate proposal to list this 
species is precluded by other higher priority listing, which we address 
below.

Preclusion and Expeditious Progress

    Preclusion is a function of the listing priority of a species in 
relation to the resources that are available and competing demands for 
those resources. Thus, in any given fiscal year (FY), multiple factors 
dictate whether it will be possible to undertake work on a proposed 
listing regulation or whether promulgation of such a proposal is 
warranted but precluded by higher-priority listing actions.
    The resources available for listing actions are determined through 
the annual Congressional appropriations process. The appropriation for 
the Listing Program is available to support work involving the 
following listing actions: proposed and final listing rules; 90-day and 
12-month findings on petitions to add species to the Lists of 
Endangered and Threatened Wildlife and Plants (Lists) or to change the 
status of a species from threatened to endangered; annual 
determinations on prior ``warranted but precluded'' petition findings 
as required under section 4(b)(3)(C)(i) of the Act; proposed and final 
rules designating critical habitat; and litigation-related, 
administrative, and program management functions (including preparing 
and allocating budgets, responding to Congressional and public 
inquiries, and conducting public outreach regarding listing and 
critical habitat). The work involved in preparing various listing 
documents can be extensive and may include, but is not limited to: 
Gathering and assessing the best scientific and commercial data 
available and conducting analyses used as the basis for our decisions; 
writing and publishing documents; and obtaining, reviewing, and 
evaluating public comments and peer review comments on proposed rules 
and incorporating relevant information into final rules. The number of 
listing actions that we can undertake in a given year also is 
influenced by the complexity of those listing actions; that is, more 
complex actions generally are more costly. For example, during the past 
several years, the cost (excluding publication costs) for preparing a 
12-month finding, without a proposed rule, has ranged from 
approximately $11,000 for one species with a restricted range and 
involving a relatively uncomplicated analysis to $305,000 for another 
species that is wide-ranging and involving a complex analysis.
    We cannot spend more than is appropriated for the Listing Program 
without violating the Anti-Deficiency Act (see 31 U.S.C. 
1341(a)(1)(A)). In addition, in FY 1998 and for each fiscal year since 
then, Congress has placed a statutory cap on funds which may be 
expended for the Listing Program, equal to the amount expressly 
appropriated for that purpose in that fiscal year. This cap was 
designed to prevent funds appropriated for other functions under the 
Act (for example, recovery funds for removing species from the Lists), 
or for other Service programs, from being used for Listing Program 
actions (see House Report 105-163, 105th Congress, 1st Session, July 1, 
1997).
    Recognizing that designation of critical habitat for species 
already listed would consume most of the overall Listing Program 
appropriation, Congress also put a critical habitat subcap in place in 
FY 2002 and has retained it each subsequent year to ensure that some 
funds are available for other work in the Listing Program: ``The 
critical habitat designation subcap will ensure that some funding is 
available to address other listing activities'' (House Report No. 107-
103, 107th Congress, 1st Session, June 19, 2001). In FY 2002 and each 
year until FY 2006, the Service has had to use virtually the entire 
critical habitat subcap to address court-mandated designations of 
critical habitat, and consequently none of the critical habitat subcap 
funds have been available for other listing activities. In FY 2007, we 
were able to use some of the critical habitat subcap funds to fund 
proposed listing determinations for high-priority candidate species; 
however, in FY 2008 we were unable to do this due to our workload for 
designating critical habitat.
    Thus, through the listing cap, the critical habitat subcap, and the 
amount of funds needed to address court-mandated critical habitat 
designations, Congress and the courts have in effect determined the 
amount of money available for other listing activities. Therefore, the 
funds in the listing cap, other than those needed to address court-
mandated critical habitat for already listed species, set the limits on 
our determinations of preclusion and expeditious progress.
    Congress also recognized that the availability of resources was the 
key element in deciding whether, when making a 12-month petition 
finding, we would prepare and issue a listing proposal or instead make 
a ``warranted but precluded'' finding for a given species. The 
Conference Report accompanying Public Law 97-304, which established the 
current statutory deadlines and the warranted-but-precluded finding, 
states (in a discussion on 90-day petition findings that by its own 
terms also covers 12-month findings) that the deadlines were ``not 
intended to allow the Secretary to delay commencing the rulemaking 
process for any reason other than that the existence of pending or 
imminent proposals to list species subject to a greater degree of 
threat would make allocation of resources to such a petition [that is, 
for a lower-ranking species] unwise.''
    In FY 2008, expeditious progress is that amount of work that could 
be achieved with $8,206,940, which is the amount of money that Congress 
appropriated for the Listing Program (that is, the portion of the 
Listing Program funding not related to critical habitat designations 
for species that are already listed). Our process is to make our 
determinations of preclusion on a nationwide basis to ensure that the 
species most in need of listing will be addressed first and also 
because we allocate our listing budget on a nationwide basis. The 
$8,206,940 was used to fund work in the following categories: 
Compliance with court orders and court-approved settlement agreements 
requiring that petition findings or listing determinations be completed 
by a specific date; section 4 (of the Act) listing actions with 
absolute statutory deadlines; essential litigation-related, 
administrative, and listing program management functions; and high-
priority listing actions. The allocations for each specific listing 
action are identified in the Service's FY 2008 Allocation Table (part 
of our administrative record).
    For FY 2009, on September 23, 2008 Congress passed a Continuing 
Resolution to operate the Federal government at the FY 2008 level of 
funding through March 6, 2009 (Pub. L.

[[Page 71823]]

110-329). Although we are currently developing the allocations for 
specific listing actions that we will fund during FY 2009, we 
anticipate funding work to comply with court orders and court-approved 
settlement agreements, work on statutorily required petition findings, 
final listing determinations for those species that were proposed for 
listing with funds from FY 2008, and continued work on proposed listing 
determinations for high-priority species.
    In FY 2007, we had more than 120 species with an LPN of 2, based on 
our September 21, 1983, guidance for assigning an LPN for each 
candidate species (48 FR 43098). Using this guidance, we assign each 
candidate an LPN of 1 to 12, depending on the magnitude of threats, 
imminence of threats, and taxonomic status; the lower the LPN, the 
higher the listing priority (that is, a species with an LPN of 1 would 
have the highest listing priority). Because of the large number of 
high-priority species, we further ranked the candidate species with an 
LPN of 2 by using the following extinction-risk type criteria: 
International Union for the Conservation of Nature and Natural 
Resources (IUCN) Red list status/rank, Heritage rank (provided by 
NatureServe), Heritage threat rank (provided by NatureServe), and 
species currently with fewer than 50 individuals, or 4 or fewer 
populations. Those species with the highest IUCN rank (critically 
endangered), the highest Heritage rank (G1), the highest Heritage 
threat rank (substantial, imminent threats), and currently with fewer 
than 50 individuals, or fewer than 4 populations, comprised a list of 
approximately 40 candidate species (``Top 40''). These 40 candidate 
species have had the highest priority to receive funding to work on a 
proposed listing determination. As we work on proposed listing rules 
for these 40 candidates, we are applying the ranking criteria to the 
next group of candidates with LPN of 2 and 3 to determine the next set 
of highest priority candidate species.
    To be more efficient in our listing process, as we work on proposed 
rules for these species in the next several years, we are preparing 
multi-species proposals when appropriate, and these may include species 
with lower priority if they overlap geographically or have the same 
threats as a species with an LPN of 2. In addition, available staff 
resources are also a factor in determining high-priority species 
provided with funding. Finally, proposed rules for reclassification of 
threatened species to endangered are lower priority, since as listed 
species, they are already afforded the protection of the Act and 
implementing regulations.
    We assigned the northern Mexican gartersnake an LPN of 3, based on 
our finding that the subspecies faces immediate and high magnitude 
threats from the present or threatened destruction, modification or 
curtailment of its habitat; predation; and the inadequacy of existing 
regulatory mechanisms. One or more of the threats discussed above are 
occurring in each known population in the United States and throughout 
historically occupied habitats in Mexico. These threats are on-going 
and, in some cases (e.g., nonnative species), considered irreversible. 
Pursuant to the 1983 Guidelines, a ``species'' facing imminent high-
magnitude threats is assigned an LPN of 1, 2, or 3 depending on its 
taxonomic status. Because the northern Mexican gartersnake is a 
subspecies, we assigned it an LPN of 3 (the highest category available 
for a subspecies). Therefore, work on a proposed listing determination 
for the northern Mexican gartersnake was, and will continue to be in 
the next year, precluded by work on higher priority candidate species 
(species with LPN of 2); listing actions with absolute statutory, court 
ordered, or court-approved deadlines; and final listing determinations 
for those species that were proposed for listing with funds from FY 
2008. This work includes all the actions listed in the tables below 
under expeditious progress.
    As explained above, a determination that listing is warranted but 
precluded must also demonstrate that expeditious progress is being made 
to add or remove qualified species to and from the Lists of Endangered 
and Threatened Wildlife and Plants. (We note that we do not discuss 
specific actions taken on progress towards removing species from the 
Lists because that work is conducted using appropriations for our 
Recovery program, a separately budgeted component of the Endangered 
Species Program. As explained above in our description of the statutory 
cap on Listing Program funds, the Recovery Program funds and actions 
supported by them cannot be considered in determining expeditious 
progress made in the Listing Program.) As with our ``precluded'' 
finding, expeditious progress in adding qualified species to the Lists 
is a function of the resources available and the competing demands for 
those funds. Our expeditious progress in FY 2008 in the Listing Program 
included preparing and publishing the following determinations:

                                        FY 2008 Completed Listing Actions
----------------------------------------------------------------------------------------------------------------
          Publication date                      Title                     Actions                FR pages
----------------------------------------------------------------------------------------------------------------
10/09/2007.........................  90-Day Finding on a          Notice of 90-day        72 FR 57278-57283.
                                      Petition to List the Black-  Petition Finding,
                                      Footed Albatross             Substantial.
                                      (Phoebastria nigripes) as
                                      Threatened or Endangered.
10/09/2007.........................  90-Day Finding on a          Notice of 90-day        72 FR 57273-57276.
                                      Petition To List the Giant   Petition Finding, Not
                                      Palouse Earthworm as         substantial.
                                      Threatened or Endangered.
10/23/2007.........................  90-Day Finding on a          Notice of 90-day        72 FR 59983-59989.
                                      Petition To List the         Petition Finding, Not
                                      Mountain Whitefish           substantial.
                                      (Prosopium williamsoni) in
                                      the Big Lost River, ID, as
                                      Threatened or Endangered.
10/23/2007.........................  90-Day Finding on a          Notice of 90-day        72 FR 59979-59983.
                                      Petition To List the         Petition Finding, Not
                                      Summer-Run Kokanee           substantial.
                                      Population in Issaquah
                                      Creek, WA, as Threatened
                                      or Endangered.
11/08/2007.........................  Response to Court on         Response to Court.....  72 FR 63123-63140.
                                      Significant Portion of the
                                      Range, and Evaluation of
                                      Distinct Population
                                      Segments, for the Queen
                                      Charlotte Goshawk.

[[Page 71824]]

 
12/13/2007.........................  12-Month Finding on a        Notice of 12-month      72 FR 71039-71054.
                                      Petition To List the         Petition Finding,
                                      Jollyville Plateau           Warranted but
                                      salamander (Eurycea          Precluded.
                                      tonkawae) as Endangered
                                      With Critical Habitat.
1/08/2008..........................  90-Day Finding on a          Notice of 90-day        73 FR 1312-1313.
                                      Petition To List the Pygmy   Petition Finding,
                                      Rabbit (Brachylagus          Substantial.
                                      idahoensis) as Threatened
                                      or Endangered.
1/10/2008..........................  90-Day Finding on Petition   Notice of 90-day        73 FR 1855-1861.
                                      To List the Amargosa River   Petition Finding,
                                      Population of the Mojave     Substantial.
                                      Fringe-Toed Lizard (Uma
                                      scoparia) as Threatened or
                                      Endangered With Critical
                                      Habitat.
1/24/2008..........................  12-Month Finding on a        Notice of 12-month      73 FR 4379-4418.
                                      Petition To List the         Petition Finding, Not
                                      Siskiyou Mountains           Warranted.
                                      Salamander (Plethodon
                                      stormi) and Scott Bar
                                      Salamander (Plethodon
                                      asupak) as Threatened or
                                      Endangered.
2/05/2008..........................  12-Month Finding on a        Notice of 12-month      73 FR 6660 6684.
                                      Petition To List the         Petition Finding,
                                      Gunnison's Prairie Dog as    Warranted.
                                      Threatened or Endangered.
02/07/2008.........................  12-Month Finding on a        Notice of Review......  73 FR 7236 7237.
                                      Petition To List the
                                      Bonneville Cutthroat Trout
                                      (Oncorhynchus clarki utah)
                                      as Threatened or
                                      Endangered.
02/19/2008.........................  Listing Phyllostegia         Proposed Listing,       73 FR 9078 9085.
                                      hispida (No Common Name)     Endangered.
                                      as Endangered Throughout
                                      Its Range.
02/26/2008.........................  Initiation of Status Review  Notice of Status        73 FR 10218 10219.
                                      for the Greater Sage-        Review.
                                      Grouse (Centrocercus
                                      urophasianus) as
                                      Threatened or Endangered.
03/11/2008.........................  12-Month Finding on a        Notice 12 month         73 FR 12929 12941.
                                      Petition To List the North   petition finding, Not
                                      American Wolverine as        warranted.
                                      Endangered or Threatened.
03/20/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 14950 14955.
                                      Petition To List the U.S.    Petition Finding,
                                      Population of Coaster        Substantial.
                                      Brook Trout (Salvelinus
                                      fontinalis) as Endangered.
04/29/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 23170 23172.
                                      Petition to List the         Petition Finding,
                                      Western Sage-Grouse          Substantial.
                                      (Centrocercus urophasianus
                                      phaios) as Threatened or
                                      Endangered.
04/29/2008.........................  90-Day Finding on Petitions  Notice of 90-day        73 FR 23173 23175.
                                      To List the Mono Basin       Petition Finding,
                                      Area Population of the       Substantial.
                                      Greater Sage-Grouse
                                      (Centrocercus
                                      urophasianus) as
                                      Threatened or Endangered.
05/06/2008.........................  Petition To List the San     Notice of 90-day        73 FR 24611 24915.
                                      Francisco Bay-Delta          Petition Finding,
                                      Population of the Longfin    Substantial.
                                      Smelt (Spirinchus
                                      thaleichthys) as
                                      Endangered.
05/06/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 24915 24922.
                                      Petition to List Kokanee     Petition Finding,
                                      (Oncorhynchus nerka) in      Substantial.
                                      Lake Sammamish,
                                      Washington, as Threatened
                                      or Endangered.
05/06/2008.........................  12-Month Finding on a        Notice of Status        73 FR 24910 24911.
                                      Petition to List the White-  Review.
                                      tailed Prairie Dog
                                      (Cynomys leucurus) as
                                      Threatened or Endangered.
05/15/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 28080 28084.
                                      Petition To List the Ashy    Petition Finding,
                                      Storm-Petrel (Oceanodroma    Substantial.
                                      homochroa) as Threatened
                                      or Endangered.
05/15/2008.........................  Determination of Threatened  Final Listing,          73 FR 28211 28303.
                                      Status for the Polar Bear    Threatened.
                                      (Ursus maritimus)
                                      Throughout Its Range;
                                      Final Rule.
05/15/2008.........................  Special Rule for the Polar   Interim Final Special   73 FR 28305 28318.
                                      Bear; Interim Final Rule.    Rule.
05/28/2008.........................  Initiation of Status Review  Notice of Status        73 FR 30596 30598.
                                      for the Northern Mexican     Review.
                                      Gartersnake (Thamnophis
                                      eques megalops).
06/18/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 34686 34692.
                                      Petition To List the Long-   Petition Finding, Not
                                      Tailed Duck (Clangula        substantial.
                                      hyemalis) as Endangered.

[[Page 71825]]

 
07/10/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 39639 39643.
                                      Petition To Reclassify the   Petition Finding,
                                      Delta Smelt (Hypomesus       Substantial.
                                      transpacificus) From
                                      Threatened to Endangered.
07/29/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 43905 43910.
                                      Petition To List the         Petition Finding,
                                      Tucson Shovel-Nosed Snake    Substantial.
                                      (Chionactis occipitalis
                                      klauberi) as Threatened or
                                      Endangered with Critical
                                      Habitat.
8/13/2008..........................  Proposed Endangered Status   Proposed Critical       73 FR 47257 47324.
                                      for Reticulated Flatwoods    Habitat, Proposed
                                      Salamander; Proposed         Listing, Endangered.
                                      Designation of Critical
                                      Habitat for Frosted
                                      Flatwoods Salamander and
                                      Reticulated Flatwoods
                                      Salamander.
9/9/2008...........................  12-month Finding on a        Notice 12 month         73 FR 52235 52256.
                                      Petition to List the         petition finding, Not
                                      Bonneville Cutthroat Trout   warranted.
                                      as Threatened or
                                      Endangered.
10/15/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 61007 61015.
                                      Petition To List the Least   Petition Finding,
                                      Chub.                        Substantial.
10/21/2008.........................  Listing 48 Species on Kauai  Proposed Listing,       73 FR 62591 62742.
                                      as Endangered and            Endangered; Proposed
                                      Designating Critical         Critical Habitat.
                                      Habitat.
10/24/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 63421 63424.
                                      Petition to List the         Petition Finding, Not
                                      Sacramento Valley Tiger      substantial.
                                      Beetle as Endangered.
10/28/2008.........................  90-Day Finding on a          Notice of 90-day        73 FR 63919 63926.
                                      Petition To List the Dusky   Petition Finding,
                                      Tree Vole (Arborimus         Substantial.
                                      longicaudus silvicola) as
                                      Threatened or Endangered.
----------------------------------------------------------------------------------------------------------------

    Our expeditious progress also included work on listing actions, 
which were funded in FY 2008, but have not yet been completed. These 
actions are listed below. We have completed all work funded in FY 2008 
on all actions under a deadline set by a court. Actions in the middle 
section of the table are being conducted to meet statutory timelines, 
that is, timelines required under the Act. Actions in the bottom 
section of the table are high priority listing actions. These actions 
include work primarily on species with an LPN of 2, and selection of 
these species is partially based on available staff resources, and when 
appropriate, include species with a lower priority if they overlap 
geographically or have the same threats as the species with the high 
priority. Including these species together in the same proposed rule 
results in considerable savings in time and funding as compared to 
preparing separate proposed rules for each of them in the future.

               Actions Funded in FY 2008 But Not Completed
------------------------------------------------------------------------
                 Species                              Action
------------------------------------------------------------------------
           Actions Subject to Court Order/Settlement Agreement
------------------------------------------------------------------------
NONE....................................  NONE.
------------------------------------------------------------------------
                    Actions with Statutory Deadlines
------------------------------------------------------------------------
Phyllostegia hispida....................  Final listing.
Yellow-billed loon......................  12-month petition finding.
Black-footed albatross..................  12-month petition finding.
Mount Charleston blue butterfly.........  12-month petition finding.
Goose Creek milk-vetch..................  12-month petition finding.
Mojave fringe-toed lizard...............  12-month petition finding.
White-tailed prairie dog................  12-month petition finding.
Pygmy rabbit (rangewide)................  12-month petition finding.
Black-tailed prairie dog................  90-day petition finding.
Lynx (include New Mexico in listing)....  90-day petition finding.
Wyoming pocket gopher...................  90-day petition finding.
Llanero coqui...........................  90-day petition finding.
American pika...........................  90-day petition finding.
Sacramento Mts. checkerspot butterfly...  90-day petition finding.
206 species.............................  90-day petition finding.
475 Southwestern species................  90-day petition finding.
------------------------------------------------------------------------
                      High Priority Listing Actions
------------------------------------------------------------------------
21 Oahu candidate species (16 plants, 5   Proposed listing.
 damselflies) (18 with LPN =2, 3 with
 LPN = 3, 1 with LPN =9).

[[Page 71826]]

 
3 southeast aquatic species (Georgia      Proposed listing.
 pigtoe, interrupted rocksnail, rough
 hornsnail) \1\ (all with LPN = 2).
Casey's june beetle (LPN = 2)...........  Proposed listing.
Sand dune lizard (LPN = 2)..............  Proposed listing.
2 southwest springsnails (Pyrgulopsis     Proposed listing.
 bernadina (LPN = 2), Pyrgulopsis
 trivialis (LPN = 2)).
3 southwest springsnails (Pyrgulopsis     Proposed listing.
 chupaderae (LPN = 2), Pyrgulopsis gilae
 (LPN = 11), Pyrgulopsis thermalis (LPN
 11)).
2 mussels (rayed bean (LPN = 2),          Proposed listing.
 snuffbox No LPN).
2 mussels (sheepnose (LPN = 2),           Proposed listing.
 spectaclecase (LPN = 4),).
Ozark hellbender \2\ (LPN = 3)..........  Proposed listing.
Altamaha spinymussel (LPN = 2)..........  Proposed listing.
4 southeast fish (rush darter (LPN = 2),  Proposed listing.
 chucky madtom (LPN = 2), Cumberland
 darter (LPN = 5), laurel dace (LPN =
 5)).
2 Colorado plants (Parchute beardtongue   Proposed listing.
 (Penstemon debilis) (LPN = 2), Debeque
 phacelia (Phacelia submutica) (LPN =
 8)).
Pagosa skyrocket (Ipomopsis polyantha)    Proposed listing.
 (LPN = 2).
------------------------------------------------------------------------
\1\ Funds for listing actions for 3 of these species were also provided
  in FY 2007.
\2\ We funded a proposed rule for this subspecies with an LPN of 3 ahead
  of other species with LPN of 2, because the threats to the species
  were so imminent and of a high magnitude that we considered emergency
  listing if we were unable to fund work on a proposed listing rule in
  FY 2008.

    We have endeavored to make our listing actions as efficient and 
timely as possible, given the requirements of the relevant law and 
regulations, and constraints relating to workload and personnel. We are 
continually considering ways to streamline processes or achieve 
economies of scale, such as by batching related actions together. Given 
our limited budget for implementing section 4 of the Act, these actions 
described above collectively constitute expeditious progress.
    The northern Mexican gartersnake will be added to the list of 
candidate species upon publication of this 12-month finding. We will 
continue to monitor the status of this species as new information 
becomes available. This review will determine if a change in status is 
warranted, including the need to make prompt use of emergency listing 
procedures.
    We intend that any proposed listing action for the northern Mexican 
gartersnake will be as accurate as possible. Therefore, we will 
continue to accept additional information and comments from all 
concerned governmental agencies, the scientific community, industry, or 
any other interested party concerning this finding.

References Cited

    A complete list of all references cited in this document is 
available upon request from the Field Supervisor at the Arizona 
Ecological Services Office (see ADDRESSES section).

Author

    The primary author of this notice is the Arizona Ecological 
Services Office (see FOR FURTHER INFORMATION CONTACT section).

Authority

    The authority for this action is section 4 of the Endangered 
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: November 12, 2008.
Kenneth Stansell,
Acting Director, U.S. Fish and Wildlife Service.
 [FR Doc. E8-27524 Filed 11-24-08; 8:45 am]
BILLING CODE 4310-55-P